Method for reactivation of platinum group metal catalyst with aqueous alkaline and/or reducing solutions

ABSTRACT

A method for reactivation of a platinum group metal catalyst which comprises treating the platinum group metal catalyst lowered in catalytic activity as the result of having been used for the catalytic reaction of hydrocarbons optionally containing an oxygen atom with at least one agent selected from an inorganic alkaline substance and a reducing substance in an aqueous medium.

This is a division of application Ser. No. 972,868, filed Dec. 26, 1978, which is a continuation-in-part application of application Ser. No. 861,521 filed Dec. 16, 1977 (now U.S. Pat. No. 4,147,660).

The present invention relates to a method for reactivation of a platinum group metal catalyst. More particularly, it relates to a method for reactivation of a platinum group metal catalyst lowered in catalytic activity as the result of having been used for the catalytic reaction of hydrocarbons optionally containing an oxygen atom.

Conventional catalysts of this type which have been used in the catalytic reaction of hydrocarbons optionally containing an oxygen atom, such as in the steam-reforming of hydrocarbons, hydro-cracking of hydrocarbons, partial oxidation of hydrocarbons and steam-reforming of alkanols, include base metal (e.g. Fe, Ni, Co) catalysts and noble metal ( e.g. Pt, Pd Ru) catalysts. In comparison with the base metal catalysts (particularly nickel catalysts), the noble metal catalysts (particularly platinum group metal catalysts) possess certain advantages as, for instance, resistance to the deposition of carbonaceous materials thereon and maintenance of high catalytic activity with use in small amounts. However, due to the expensiveness of the noble metal catalysts, the practical considerations have been concentrated in the use of the base metal catalysts. In order to overcome this shortcoming, attempts have been made to reactivate noble metal catalysts lowered in the catalytic activity so as to enable their reuse. Typical conventional procedures for such reactivation include treatment with hydrogen, steam or oxygen, and in fact, such procedures are quite effective in the elimination of certain poisonous materials in addition to the carbonaceous materials deposited on the catalysts. However, the recovery of the catalytic activity provided by these procedures is frequently not satisfactory.

In general, catalytic reactions of hydrocarbons optionally containing an oxygen atom in the presence of a platinum group metal catalyst result in deposition of various materials such as carbonaceous materials and sulfurous materials on the catalyst particles. In addition, these catalytic reactions often result in a sintering of the catalyst particles causing their mutual cohesion, whereby the particle size of the catalyst enlarged and the dispersibility of the catalyst consequently lowered. Further, the physical and chemical constitutions and behaviors of the catalysts may be gradually changed during the catalytic reactions. Due to these and other factors which are still unclear, the catalytic activity of the catalyst is lowered during the course of the catalytic reaction. In order for recovery of the catalytic activity to reach a practically satisfactory level, it is necessary to substantially reduce or eliminate these adverse factors.

As the result of extensive study, it has now been found that treatment of platinum group metal catalysts lowered in catalytic activity by contact with at least one agent selected from an inorganic alkaline substance and a reducing substance in an aqueous medium provides an effective recovery of the catalytic activity. It has also been found that the combination of treatments with both an inorganic alkaline substance in an aqueous medium and a reducing substance in an aqueous medium is particularly effective for accomplishment of the reactivation. It has further been found that the reactivation effected by the treatment with the inorganic alkaline substance and/or the reducing substance can be more assured by treating the catalyst lowered in catalytic activity with hydrogen, steam or oxygen before or after the treatment with the inorganic alkaline substance and/or the reducing substance.

It may be noted that conventional treatment with hydrogen, steam or oxygen is effective for the removal of carbonaceous materials deposited on the catalyst but not for the elimination of sulfurous materials. On the other hand, treatment with an inorganic alkaline substance or a reducing substance is highly effective for the removal of sulfurous materials though the effect of elimination of carbonaceous materials may not be as high as obtained by conventional treatment with hydrogen, steam or oxygen. Particularly notable is the fact that while the conventional treatment has almost no effect on the recovery of the lowered catalytic activity, treatment with an inorganic alkaline substance or a reducing substance has a surprisingly significant effect.

According to the present invention, the reactivation of a platinum group metal catalyst lowered in the catalytic activity is carried out by treatment of the catalyst with at least one inorganic alkaline substance or at least one reducing substance of both, in an aqueous medium.

The platinum group metal catalyst to be subjected to the treatment in the present invention may be the one which comprises a platinum group metal such as ruthenium, rhodium, palladium, osmium, iridium or platinum as the catalyst component deposited on a carrier material such as alumina, magnesia, zirconia, titania, silica, silica-alumina, silica-magnesia, alumina-magnesia or carbon and lowered in catalytic activity as the result of having been used for the catalytic reaction of hydrocarbons optionally containing an oxygen atom. In addition to the said essential catalyst component, the platinum group metal catalyst may comprise any additive which does not materially afford any unfavorable influence thereon. Examples of the additive include any material known as the so-called "co-catalyst" such as alkali metals, alkaline earth metals, iron, copper, nickel, cobalt, chromium, tungsten, manganese or molybdenum. The term "hydrocarbons optionally containing an oxygen atom" hereinabove used is intended to mean organic compounds consisting of carbon atoms and hydrogen atoms or of carbon atoms, hydrogen atoms and oxygen atoms, and their examples include aliphatic hydrocarbons, aromatic hydrocarbons, naphthenic hydrocarbons, alkanols, alkanones, etc. Examples of the catalytic reaction are steam-reforming of hydrocarbons, hydro-cracking of hydrocarbons, partial oxidation of hydrocarbons, steam-reforming of alkanols, etc.

The inorganic alkaline substance may be an inorganic alkaline compound containing at least one alkali metal or alkaline earth metal. Examples of the alkali metals and the alkaline earth metals are sodium, potassium, calcium, magnesium, barium, strontium, etc. Preferred examples of the inorganic alkaline compounds containing these alkali metals and alkaline earth metals are hydroxides, carbonates, nitrates, sulfates, etc. or mixtures thereof. The concentration of the inorganic alkaline substance in the aqueous medium may be varied depending upon the amount of the catalyst component deposited on the carrier material, the degree of lowered catalytic activity, the temperature and pressure at which the reactivation treatment is carried out and the like. In general, however, the concentration is usually from about 0.001 to 10 N, preferably from about 0.001 to 5 N.

As the reducing substance, there may be employed normally water-soluble or water-dispersible reducing substances such as hydrazine, formaldehyde, sodium borohydride, lithium aluminum hydride, sodium tartrate, potassium tartrate, sodium potassium tartrate, calcium tartrate, sodium hydrogen tartrate, sodium formate, potassium formate, calcium formate, glucose, etc. or mixtures thereof. The concentration of the reducing substance in the aqueous medium depends on the amount of the catalyst component deposited on the carrier material, the degree of lowered catalytic activity, the temperature and pressure employed in the reactivation treatment, etc. Normally it falls in the range of about 0.01% to 10% by weight.

Even when the catalyst lowered in catalytic activity is treated solely with the inorganic alkaline substance or the reducing substance, appreciable elimination of sulfurous materials deposited on the catalyst and considerable recovery of the catalytic activity can be attained by choosing appropriate conditions for the treatment. In general, however, the treatment is preferably carried out in two separate steps, i.e. by treatment with the inorganic substance and then treatment with the reducing substance, or vice versa. When desired, such a two step treatment may be repeatedly applied until a satisfactory recovery of the catalytic activity is achieved, though a single application of two step treatment is usually sufficient.

The treatment with the inorganic alkaline substance is usually effected at room temperature (i.e. about 5 to 30° C.) or while heating under atmospheric pressure or an elevated pressure. However, it can be widely varied depending on the extent of lowered catalytic activity, the composition of the catalyst, the kind of the inorganic alkaline substance employed, etc. In general, a higher temperature affords a better result, but too high a temperature should be avoided since the carrier material may be unfavorably dissolved. Thus, the temperature is usually from about 5 to 250° C., preferably from about 50 to 200° C. The pressure may be appropriately selected so as to maintain the system for treatment in a liquid state, and such pressure do not usually exceed 50 kg/cm².

Treatment with the reducing substance may be carried out at a temperature from room temperature to the decomposition temperature of the reducing substance under atmospheric pressure or at an elevated pressure. Although the temperature is considerably affected by various factors such as the extent to which the catalytic activity is lowered, the composition of the catalyst and the kind of the reducing substance, the temperature is ordinarily between room temperature and about 250° C., insofar as the reducing substance is not decomposed. The pressure may be appropriately selected so as to keep the system in a liquid state and is normally not higher than 50 kg/cm².

When combined two step treatments with the inorganic alkaline substance and with the reducing substance are effected in this order or vice versa, these may be performed with or without intervention of water-washing and/or drying between them.

The treatment(s) with the inorganic alkaline substance and/or with the reducing substance may be effected until a satisfactory recovery of the catalytic activity is attained. Usually, treatment(s) effected so as to eliminate not less than about 40% of carbonaceous materials and not less than about 70% of sulfurous materials deposited on the catalyst will achieve the satisfactory recovery of the catalytic activity. The contact or treating time employed will vary depending upon many factors such as whether one or two step treatments are used, the degree of recovery of catalytic activity desired, etc. Usually a treating time of several minutes to several tens hours (e.g. 3 minutes to 80 hours) is generally sufficient to achieve the aforementioned satisfactory recovery of catalytic activity. However, as stated above, the deterioration of the catalytic activity is caused not only by deposition of carbonaceous and/or sulfurous materials but also by other unclear factors, and therefore the elimination of the said deposited materials may not always be sufficient for recovery of the catalytic activity. If necessary, therefore, the said treatment(s) with the inorganic alkaline substance and/or with the reducing substance may be carried out in combination with any conventional reactivation treatment. For instance, the treatment of the catalyst with hydrogen, steam or oxygen may be effected prior to, between or subsequent to the treatment(s) with the inorganic alkaline substance and/or with the reducing substance.

Examples of usable gases for the conventional reactivation treatment are hydrogen, oxygen, steam, a mixture of hydrogen and steam, a mixture of oxygen and steam, etc. These gases may be optionally diluted with any other inert gas such as nitrogen, helium or argon. Particularly preferred are (1) hydrogen, (2) a mixture of hydrogen and steam having a hydrogen content of not less than about 30 mol%, (3) a mixture of steam and a gaseous diluent having a steam content of not less than about 30 mol%, (4) a mixture of oxygen and a gaseous diluent having an oxygen content of not less than about 0.5% by volume, (5) a mixture of oxygen, steam and a gaseous diluent having an oxygen content of not less than about 0.5% by volume and a steam content of not less than about 30% by volume, etc.

The conditions for treatment with the said gases depend on the amount of the catalyst component deposited on the carrier material, the deposited amount of poisonous materials (particularly carbonaceous material), the concentration of the active gases, the kind of other treatment procedures employed, etc. Usually a temperature of about 350 to 750° C. and a pressure of about 1 to 50 atm. (absolute) are adopted. The treatment may be continued until the deposited amount of poisonous materials, particularly carbonaceous materials, is appreciably decreased. When the deposited amount of carbonaceous materials is relatively large, the generation of heat occurs sometimes. In such case, the oxygen content in the treating gases may be decreased or the use of the treating gases containing no oxygen is preferred.

After the finalization of the treatment(s) as explained above, the resulting catalyst may be washed with water and/or dried. Particularly, when the final step is the treatment with the inorganic alkaline substance or the reducing agent in an aqueous medium, water washing and drying are favorable.

As stated above, the thus reactivated catalyst is satisfactorily recovered in catalytic activity. Even when the catalyst is severely positioned and its catalytic activity is extremely lowered, the repeated application of the above treatment(s) enables the satisfactory recovery of catalytic activity nearly equal to that of a freshly prepared catalyst. Further, when the once reactivated catalyst is lowered again in the catalytic activity, the repeated application of the above treatment(s) will reactivate it. Thus, the present invention is quite advantageous in making it possible to use an expensive platinum group metal catalyst repeatedly.

Practical and presently preferred embodiments of the present invention are illustratively shown in the following Examples wherein part(s) and % are by weight unless otherwise indicated. The amount of the catalyst required for reaction indicates a minimum amount of the catalyst required for showing a catalytic activity for reaction.

EXAMPLE 1

A catalyst comprising 2.0% of ruthenium and 0.1% of chromium oxide deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₁ ") (325 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising naphtha (content of sulfur, 2 ppm; final boiling point, 168° C.), steam, hydrogen, methane and carbon oxides was fed therein to effect continuously steam-reforming reaction for 1500 hours under the following conditions:

Temperature of reactor: inlet, 450° C., outlet, 524° C.;

Space velocity: 2000 (1/hr);

Ratio of steam/hydrocarbon: 0.9 (number of oxygen atoms per one carbon atom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 1500 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₁ ") was treated under the conditions as shown in Table 1 for reactivation. The reactivated catalyst was reused in steam-reforming reaction under the same conditions as mentioned above. The results are shown in Table 1.

As seen from Table 1, the reactivation treatment with hydrogen is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalysts C₁ -1 and C₁ -2). In the case of treatment with an inorganci alkaline substance, elimination of sulfurous materials and recovery of the dispersibility as well as recovery of the catalytic activity are good.

                                      TABLE 1                                      __________________________________________________________________________                      Reactivated                                                   Catalyst    A.sub.1                                                                           B.sub.1                                                                          C.sub.1 -1                                                                        C.sub.1 -2                                                                          D.sub.1 -1                                                                         D.sub.1 -2                                                                         D.sub.1 -3                                                                         D.sub.1 -4                                                                         D.sub.1 -5                                                                         D.sub.1 -6                        __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          -- --                                                                               H.sub.2                                                                           O.sub.2 :N.sub.2                                                                    0.375N                                                                             0.375N                                                                             0.375N                                                                             1.0N                                                                               5.0N                                                                               0.375N                            tions                                                                               agent*         (= 21:                                                                              NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                 of                  79 by                                                      treat-              volume)                                                    ment                                                                           for  Temper-                                                                               -- --                                                                               650                                                                               500  50  70  100 100 70  100                               reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              -- --                                                                               6.0                                                                               6.0  1.0 1.0 1.0 1.0 1.0 1.0                                    (ata)                                                                          Time (hrs)                                                                            -- --                                                                               12 5    6.0 3.0 1.5 0.75                                                                               0.5 3.0                               Post-treat- -- --                                                                               -- --   Water washing: 100° C., 2 hrs.                 ment                     Drying: 100° C., 16 hrs.                       Elimina                                                                             Carbo- -- --                                                                                100                                                                              100  41  46  55  54  59  54                                tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- --                                                                               33 40   78  84  95  97  100 93                                materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43 20                                                                               19 17   28                                                                               30                                                                               35  37  37      36                                (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         52.5                                                                              --                                                                               -- --   85                                                                               68                                                                               63  63  61      64                                required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________      *In case of Catalysts C.sub.1 -1 and C.sub.1 -2, the treatment was carrie      out with a space velocity of 2500 (l/hr)                                 

    Reactivated                                                                                Catalyst    D.sub.1 -7                                                                         D.sub.1 -8                                                                          D.sub.1 -9                                                                          D.sub.1 -10                                                                        D.sub.1 -11                                                                        D.sub.1 -12                      __________________________________________________________________________                 Condi-                                                                              Reactivation                                                                          0.375N                                                                             0.375N                                                                              0.375N                                                                              0.375N                                                                             0.375N                                                                             0.001N                                       tions                                                                               agent  KOH Ba(OH).sub.2                                                                        Sr(OH).sub.2                                                                        NaOH                                                                               NaOH                                                                               NaOH                                         of                                                                             treat-                                                                         ment                                                                           for  Temper-                                                                               100 100  100  148 205 100                                          reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0  1.0  5.0 20.0                                                                               1.0                                               (ata)                                                                          Time (hrs)                                                                            3.0 3.0  3.0  1.0 0.5 10.0                                              Post-treat-                                                                           Water washing: 100° C., 2 hrs.                                   ment   Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 52  50   48   56  58  40                                           tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             90  87   87   100 100 80                                           materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      35  33   32   34  37  30                                           (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         64  66   68   63  60  69                                           required for reac-                                                             tion (ml)                                                          __________________________________________________________________________

EXAMPLE 2

A catalyst comprising 0.3% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (1000 ml) was charged into a tubular reactor of 1 inch in diameter, and naphtha (final boiling point, 108° C.) and hydrogen were fed therein to effect continuously hydro-cracking reaction under the following conditions:

Temperature of reactor at inlet: 265° C.;

Pressure: 46 atm. (absolute);

Ratio of hydrogen/hydrocarbon: 1.20 (by mol)

Mass velocity: 500 kg-mol/m².hr.

The conversion of hydrogen at the initial stage was 82%, and the catalytic activity was materially decreased after about 200 hours. The resultant catalyst was heated in a 0.375 N aqueous solution of sodium hydroxide at 100° C. for 3 hours, washed with water at 100° C. for 2 hours and then dried at 100° C. for 16 hours. The thus reactivated catalyst was reused for hydro-cracking under the same conditions as above, whereby a conversion of hydrogen of 80% was observed.

EXAMPLE 3

A catalyst comprising 2.6% of ruthenium and 0.1% of chromium oxide deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₂ ") (325 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising naphtha (content of sulfur, 2 ppm; final boiling point, 168° C.), steam, hydrogen, methane and carbon oxides was fed therein to effect continuously steam-reforming reaction for 2400 hours under the following conditions:

Temperature of reactor: inlet, 400° C., outlet, 517° C.;

Space velocity: 1500 (1/hr);

Ratio of steam/hydrocarbon: 0.7 (number of oxygen atoms per one carbon atom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 2400 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₂ ") was treated under the conditions as shown in Table 2 for reactivation. The reactivated catalyst was reused in steam-reforming reaction under the same conditions as mentioned above. The results are shown in Table 2.

As seen from Table 2, the reactivation treatment with hydrogen is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalyst C₂). In the case of treatment with an inorganic alkaline substance at room temperature, elimination of sulfurous materials and recovery of the dispersibility are relatively good when the treating time is long, but the recovery of the catalytic activity is insufficient (Catalysts D₂ -1 and D₂ -2). The treatment with an inorganic alkaline substance under heating is proved to be effective for recovery of the catalytic activity (Catalysts D₂ -3 to D₂ -5). In the treatment with a reducing substance, elimination of sulfurous material is good, but removal of carbonaceous materials is hardly attained. There is a tendency to recovery of the catalytic activity (Catalysts D₂ -6 to D₂ -13).

                                      TABLE 2                                      __________________________________________________________________________                     Reactivated                                                    Catalyst    A.sub.2                                                                          B.sub.2                                                                          C.sub.2                                                                           D.sub.2 -1                                                                         D.sub.2 -2                                                                         D.sub.2 -3                                                                         D.sub.2 -4                                                                         D.sub.2 -5                                                                         D.sub.2 -6                                                                         D.sub.2 -7                          __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          --                                                                               --                                                                               H.sub.2                                                                           0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.4%                                                                               0.3%                                tions                                                                               agent*        NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               Hydra-                                                                             Lithium                             of                                     zine                                                                               aluminum                            treat                                      hydride                             ment                                                                           for  Temper-                                                                               --                                                                               --                                                                               650                                                                               30  30  50  100 148 20  20                                  reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              --                                                                               --                                                                               6.0                                                                               1.0 1.0 1.0 1.0 5.0 1.0 1.0                                      (ata)                                                                          Time (hrs)                                                                            --                                                                               --                                                                               12.0                                                                              3.0 10.0                                                                               6.0 3.0 1.0 3.0 3.0                                      Post-treat-                                                                           --                                                                               --                                                                               -- Water washing: 100° C., 2 hrs.                                                              Water washing:                               ment          Drying: 100° C., 16 hrs.                                                                    75° C., 3 hrs                                                           Drying: 100° C.,                                                        16 hrs.                                 Elimina-                                                                            Carbo- --                                                                               --                                                                               100 12 41  43  52  56  0   0                                   tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of -poisonous                                                                       Sulfurous                                                                             --                                                                               --                                                                               31  32 72  78  90  100 68  49                                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43                                                                               17                                                                               17 21  27  28  34  35  21  23                                  (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         92                                                                               --                                                                               -- --  --  147 110 106 276 270                                 required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________      *In case of Catalyst C.sub.2, the treatment was carried out with a space       velocity of 2500 (l/hr).                                                 

    Reactivated                                                                             Catalyst    D.sub.2 -8                                                                         D.sub.2 -9                                                                          D.sub.2 10                                                                          D.sub.2 -11                                                                        D.sub.2 -12                                                                         D.sub.2 -13                        __________________________________________________________________________              Condi-                                                                              Reactivating                                                                          0.7%                                                                               2.0% 0.3% 1.0%                                                                               1.0% 1.0%                                        tions                                                                               agent  Sodium                                                                             Sodium                                                                              Glucose                                                                             Hydra-                                                                             Formal-                                                                             Sodium                                      of          tart-                                                                              formate   zine                                                                               dehyde                                                                              boro-                                       treat-      rate                   hydride                                     ment                                                                           for  Temper-                                                                               20  20   20   60  60   60                                          reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0  1.0  1.0 1.0  1.0                                              (ata)                                                                          Time (hrs)                                                                            3.0 3.0  3.0  3.0 3.0  3.0                                              Post-treat-                                                                           Water washing: 75° C., 3 hrs.                                    ment   Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 0   0    0    0   0    0                                           tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             46  53   49   90  67   88                                          materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      23  23   23   23  23   23                                          (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         272 272  276  266 270  276                                         required for reac-                                                             tion (ml)                                                             __________________________________________________________________________

EXAMPLE 4

The reactivated catalysts as obtained in Example 3 (Catalysts D₂ -1 to D₂ -4 and D₂ -6 to D₂ -12) were each subjected to further treatment for reactivation under the conditions as shown in Table 3. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 3. The results are shown in Table 3.

As seen from Table 3, the catalysts (E₃ -1 to E₃ -20) reactivated in two steps are much more recovered in catalytic activity than the catalysts (D₂ -1 to D₂ -4 and D₂ -6 to D₂ -12) reactivated in one step.

                                      TABLE 3                                      __________________________________________________________________________     Catalyst    E.sub.3 -1                                                                           E.sub.3 -2                                                                           E.sub.3 -3                                                                          E.sub.3 -4                                                                          E.sub.3 -5                                                                           E.sub.3 -6                                                                          E.sub.3 -7                                                                          E.sub.3 -8                                                                          E.sub.3 -9                                                                         E.sub.3 -10         Catalyst used                                                                              D.sub.2 -1                                                                           D.sub.2 -2                                                                           D.sub.2 -3                                                                          D.sub.2 -3                                                                          D.sub.2 -4                                                                           D.sub.2 -4                                                                          D.sub.2 -6                                                                          D.sub.2 -6                                                                          D.sub.2 -11                                                                        D.sub.2             __________________________________________________________________________                                                                -12                 Condi-                                                                              Reactivating                                                                          1.0%  0.4%  0.4% 0.5% 0.4%  0.3% 0.375N                                                                              0.375N                                                                              0.375N                                                                             0.375N              tions                                                                               agent  Hydra-                                                                               Hydra-                                                                               Hydra-                                                                              Formal-                                                                             Hydra-                                                                               Sodium                                                                              NaOH NaOH NaOH                                                                               NaOH                of          zine  zine  zine dehyde                                                                              zine  boro-                                  treat-                                  hydride                                ment                                                                           for  Temper-                                                                               60    20    20   20   20    20   50   100  100 80                  reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0   1.0   1.0  1.0  1.0   1.0  1.0  1.0  1.0 1.0                      (ata)                                                                          Time (hrs)                                                                            3.0   3.0   3.0  3.0  3.0   3.0  6.0  3.0  3.0 3.0                 Post-treat- Water washing: 75° C., 3 hrs.                                                                            Water washing: 100°                                                     C., 2 hrs.                        ment        Drying: 100° C., 16 hrs.  Drying: 100° C., 16                                                     hrs.                              Elimina-                                                                            Carbo- 12    41    43   43   52    52   43   54   53  47                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             89    91    93   93   97    95   91   97   95  89                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      34    36    36   36   40    40   35   39   41  39                  (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         108   110   102  106  95    98   102  95   93  95                  required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________     Catalyst    E.sub.3 -11                                                                          E.sub.3 -12                                                                          E.sub.3 -13                                                                         E.sub.3 -14                                                                         E.sub.3 -15                                                                          E.sub.3 -16                                                                         E.sub.3 -17                                                                         E.sub.3 -18                                                                         E.sub.3 -19                                                                        E.sub.3 -20         Catalyst used                                                                              D.sub.2 -1                                                                           D.sub.2 -2                                                                           D.sub.2 -3                                                                          D.sub.2 -3                                                                          D.sub.2 -4                                                                           D.sub.2 -4                                                                          D.sub.2 -7                                                                          D.sub.2 -8                                                                          D.sub.2 -9                                                                         D.sub.2             __________________________________________________________________________                                                                -10                 Condi-                                                                              Reactivating                                                                          0.3%  0.3%  0.7% 2.0% 0.3%  0.3% 0.375N                                                                              0.1N 0.375N                                                                             0.375N              tions                                                                               agent  Lithium                                                                              Lithium                                                                              Sodium                                                                              Sodium                                                                              Lithium                                                                              Glucose                                                                             NaOH NaOH NaOH                                                                               NaOH                of          aluminum                                                                             aluminum                                                                             tart-                                                                               formate                                                                             aluminum                                     treat-      hydride                                                                              hydride                                                                              rate      hydride                                      ment                                                                           for  Temper-                                                                               20    20    20   20   20    20   50   100  100 80                  reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0   1.0   1.0  1.0  1.0   1.0  1.0  1.0  1.0 1.0                      (ata)                                                                          Time (hrs)                                                                            3.0   3.0   3.0  3.0  3.0   3.0  6.0  3.0  1.5 3.0                      Post-treat-                                                                           Water washing: 75° C., 3 hrs.                                                                            Water washing: 100°                                                     C., 2 hrs.                             ment   Drying: 100° C., 16 hrs.  Drying: 100° C., 16                                                     hrs.                              Elimina-                                                                            Carbo- 12    41    43   43   52    52   43   44   46  47                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             66    86    89   90   95    95   89   88   93  92                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      31    36    37   37   41    40   38   37   37  37                  (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         126   106   100  100  94    95   98   100  100 100                 required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________

EXAMPLE 5

The reactivated catalyst obtained in Example 3 (Catalyst D₂ -3) was treated with a 0.4% aqueous solution of hydrazine at 20° C. under 1 atm. (absolute) for 3 hours, washed with water at 75° C. for 3 hours and dried at 100° C. for 16 hours. Then, the resulting catalyst was again subjected to treatment with a 0.375 N aqueous solution of sodium hydroxide at 50° C. under 1 atm. (absolute) for 6 hours and treatment with a 0.4% aqueous solution of hydrazine at 20° C. under 1 atm. (absolute) for 3 hours, followed by washing with water at 75° C. for 3 hours and drying at 100° C. for 16 hours. The thus reactivated catalyst was used for steam-reforming under the same conditions as stated in Example 3. The results are as follows: elimination percentage of poisonous materials: carbonaceous materials, 75%; sulfurous material, 100%. Specific surface area: 42 m² /g-Ru. Amount of catalyst required for reaction: 93 ml.

As seen from the above results, the repeating treatments with an inorganic alkaline substance and with a reducing substance are quite effective for reactivation of the catalyst.

EXAMPLE 6

The reactivated catalyst obtained in Example 3 (Catalyst D₂ -3) was treated with a 0.7% aqueous solution of sodium tartrate at 20° C. under 1 atm. (absolute) for 3 hours, washed with water at 75° C. for 3 hours and dried at 100° C. for 16 hours. Then, the resulting catalyst was again subjected to treatment with a 0.375 N aqueous solution of sodium hydroxide at 50° C. under 1 atm. (absolute) for 6 hours and treatment with a 0.7% aqueous solution of sodium tartrate at 20° C. under 1 atm. (absolute) for 3 hours, followed by washing with water at 75° C. for 3 hours and drying at 100° C. for 16 hours. The thus reactivated catalyst was used for steam-reforming under the same conditions as stated in Example 3. The results are as follows: elimination percentage of poisonous materials: carbonaceous materials, 70%; sulfurous material, 100%. Specific surface area: 42 m² /g-Ru. Amount of catalyst required for reaction: 93 ml.

As seen from the above results, the repeating treatments with an inorganic alkaline substance and with a reducing substance are quite effective for reactivation of the catalyst.

EXAMPLE 7

A catalyst comprising 3.8% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter (hereinafter referred to as "Catalyst A₄ ") (325 ml) was charged into a tubular reactor of 1 inch in diameter, and naphtha (content of sulfur, 2 ppm; final boiling point, 220° C.) and steam were fed therein to effect continuously steam-reforming reaction for 750 hours under the following conditions:

Temperature of reactor: inlet, 510° C., outlet, 518° C.;

Space velocity: 2000 (1/hr);

Ratio of steam/hydrocarbon: 1.9 (number of oxygen atoms per one carbon atom in the feeding gaseous materials);

Pressure: 13 atm. (absolute)

After 750 hours, the catalyst (hereinafter referred to as "Catalyst B₄ ") was treated under the same conditions as shown in Table 4 for reactivation. The reactivated catalyst was reused in steam-reforming reaction under the same conditions as mentioned above. The results are shown in Table 4.

As seen from Table 4, treatment with an inorganic alkaline substance shows recovery of the catalytic activity, and treatment with a reducing substance shows a tendency to recovery of the catalytic activity. However, when the catalyst is severely polluted, an elevated temperature is necessary for satisfactory recovery of the catalytic activity by treatment with an inorganic alkaline substance.

                                      TABLE 4                                      __________________________________________________________________________                             Reactivated                                            Catalyst    A.sub.4                                                                              B.sub.4                                                                              C.sub.4                                                                              D.sub.4 -1                                                                           D.sub.4 -2                                                                           D.sub.4 -3                                                                          D.sub.4 -4                                                                          D.sub.4 -5                                                                          D.sub.4 -6            __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          --    --    H.sub.2                                                                              0.375N                                                                               0.375N                                                                               0.375N                                                                              0.4% 1.0% 1.0%                  tions                                                                               agent                    NaOH  NaOH  NaOH Hydra-                                                                              Formal-                                                                             Sodium                                                                         -of        zine d                                                              ehyde boro-           treat-                                                   hydride               ment                                                                           for  Temper-                                                                               --    --    650   30    50    100  20   60   60                    reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              --    --    6.0   1.0   1.0   1.0  1.0  1.0  1.0                        (ata)                                                                          Time (hrs)                                                                            --    --    12.0  3.0   6.0   3.0  3.0  3.0  3.0                        Post-treat-                                                                           --    --    --    Water washing: 100° C.,                                                                  --   --   --                         ment                     2 hrs.                                                                         Drying: 100° C., 16 hrs.                  Elimina-                                                                            Carbo- --    --    100   10    41    56   0    0    0                     tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             --    --    29    30    80    94   72   71   90                    materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43    20    19    23    29    36   23   26   26                    (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         91    --    --    --    145   109  270  264  270                   required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________                 Reactivated                                                        Catalyst    D.sub.4 -7                                                                           D.sub.4 -8                                                                           D.sub.4 -9                                                                           D.sub.4 -10                                                                          D.sub.4 -11                                                                          D.sub.4 -12                                                                         D.sub.4 -13                                                                         D.sub.4 -14                                                                         D.sub.4 -15           __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          0.375N                                                                               0.375N                                                                               0.375N                                                                               0.1N  0.375N                                                                               0.375N                                                                              0.5% 0.3% 0.3% l-tions agen                                                              t Na.sub.2                                                                     CO.sub.3 Ba(OH).s                                                              ub.2 Sr(OH).sub.2                                                              5Na.sub.2                                                                      CO.sub.3 Ba(OH).s                                                              ub.2 Sr(OH).sub.2                                                               Formal- Sodium L                                                              ithium                of                                             dehyde                                                                              boro-                                                                               aluminum              treat-                                              hydride                                                                             hydride               ment                                                                           for  Temper-                                                                               100   100   100   100   80    100  20   20   20                    reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0   1.0   1.0   1.0   1.0   1.0  1.0  1.0  1.0                        (ata)                                                                          Time (hrs)                                                                            3.0   3.0   3.0   3.0   3.0   1.0  3.0  3.0  3.0                        Post-treat-                                                                           Water washing: 100° C., 2 hrs.                                                                             Water washing: 75°                                                      C., 3 hrs.                           ment   Drying 100° C., 16 hrs.     Drying: 100° C., 16                                                     hrs.                            Elimina-                                                                            Carbo- 54    51    50    44    49    46   0    0    0                     tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             91    89    86    77    80    79   56   70   51                    materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      36    35    35    32    32    31   23   23   26                    (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         111   114   119   123   126   129  274  278  260                   required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________                                                      Reactivated                                                        Catalyst    D.sub.4 -16                                                                        D.sub.4 -17                                                                         D.sub.4              __________________________________________________________________________                                                               -18                                                       Condi-                                                                              Reactivating                                                                          0.7%                                                                               2.0% 0.3%                                                      tions                                                                               agent  Sodium                                                                             Sodium                                                                              Glucose                                                   of          tart-                                                                              formate                                                        treat-      rate                                                               ment                                                                           for  Temper-                                                                               20  20   20                                                        reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0  1.0                                                            (ata)                                                                          Time (hrs)                                                                            3.0 3.0  3.0                                                            Post-treat-                                                                           Water washing:                                                                 75° C., 3 hrs.                                                   ment   Drying: 100° C.,                                                        16 hrs.                                                            Elimina-                                                                            Carbo- 0   0    0                                                         tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             49  57   52                                                        materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      26  25   23                                                        (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         264 264  270                                                       required for reac-                                                             tion (ml)                                 __________________________________________________________________________

EXAMPLE 8

The reactivated catalysts as obtained in Example 7 (Catalysts D₄ -1 to D₄ -3, D₄ -8 and D₄ -10 to D₄ -18) were each subjected to further treatment for reactivation under the conditions as shown in Table 5. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 7. The results are shown in Table 5.

As seen from Table 5, the catalysts (E₅ -1 to E₅ -19) reactivated in two steps are much more recovered in catalytic activity than the catalysts (D₄ -1 to D₄ -3, D₄ -8 and D₄ -10 to D₄ -18) reactivated in one step.

                                      TABLE 5                                      __________________________________________________________________________     Catalyst    E.sub.5 -1                                                                          E.sub.5 -2                                                                         E.sub.5 -3                                                                          E.sub.5 -4                                                                          E.sub.5 -5                                                                          E.sub.5 -6                                                                         E.sub.5 -7                                                                          E.sub.5 -8                                                                         E.sub.5 -9                                                                         E.sub.5 -10               Catalyst used                                                                              D.sub.4 -1                                                                          D.sub.4 -3                                                                         D.sub.4 -8                                                                          D.sub.4 -8                                                                          D.sub.4 -10                                                                         D.sub.4 -11                                                                        D.sub.4 -12                                                                         D.sub.4 -13                                                                        D.sub.4 -13                                                                        D.sub.4 -14               __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          1.0% 0.4%                                                                               0.5% 0.5% 0.5% 1.0%                                                                               0.3% 0.375N                                                                             0.1N                                                                               0.375N                    tions                                                                               agent  Sodium                                                                              Hydra-                                                                             Formal-                                                                             Formal-                                                                             Formal-                                                                             Hydra-                                                                             Sodium                                                                              NaOH                                                                               NaOH                                                                               KOH                       of          boro-                                                                               zine                                                                               dehyde                                                                              dehyde                                                                              dehyde                                                                              zine                                                                               boro-                                  treat-      hydride                     hydride                                ment                                                                           for  Temper-                                                                               60   20  20   60   20   60  20   100 100 80                        reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0  1.0 1.0  1.0  1.0  1.0 1.0  1.0 1.0 1.0                            (ata)                                                                          Time (hrs)                                                                            3.0  3.0 3.0  3.0  3.0  3.0 3.0  3.0 3.0 3.0                            Post-treat-                                                                           Water washing: 75° C., 3 hrs.                                                                            Water washing: 100°                                                     C.,                                    ment   Drying: 100° C., 16 hrs.  2 hrs.                                                                         Drying: 100° C., 16                                                     hrs.                              Elimina-                                                                            Carbo- 10   56  51   51   44   49  46   54  44  52                        tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             86   96  95   97   89   96  90   86  80  85                        materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      36   41  41   41   36   41  35   41  36  36                        (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         109  93  97   93   106  97  116  95  102 106                       required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________     Catalyst    E.sub.5 -11                                                                         E.sub.5 -12                                                                         E.sub.5 -13                                                                          D.sub.5 -14                                                                         E.sub.5 -15                                                                          E.sub.5 -16                                                                        E.sub.5 -17                                                                        E.sub.5 -18                                                                         D.sub.5 -19                Catalyst used                                                                              D.sub.4 -1                                                                          D.sub.4 -2                                                                          D.sub.4 -10                                                                          D.sub.4 -11                                                                         D.sub.4 -12                                                                          D.sub.4 -15                                                                        D.sub.4 -16                                                                        D.sub.4 -17                                                                         D.sub.4 -18                __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          0.7% 0.3% 0.3%  2.0% 0.3%  0.1N                                                                               0.1N                                                                               0.375N                                                                              0.375N                     tions                                                                               agent  Sodium                                                                              Glucose                                                                             Lithium                                                                              Sodium                                                                              Lithium                                                                              NaOH                                                                               Na.sub.2 CO.sub.                                                                   Ba(OH).sub.2                                                                        Sr(OH).sub.2               of          tart-     aluminum                                                                             formate                                                                             aluminum                                      treat-      rate      hydride    hydride                                       ment                                                                           for  Temper-                                                                               20   20   20    20   20    100 100 80   100                        reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0  1.0  1.0   1.0  1.0   1.0 1.0 1.0  1.0                             (ata)                                                                          Time (hrs)                                                                            3.0  3.0  3.0   3.0  3.0   3.0 3.0 3.0  1.0                             Post-treat-                                                                           Water washing: 75° C., 3 hrs.                                                                      Water washing: 100° C., 2                                               hrs.                                         ment   Drying: 100° C., 16 hrs.                                                                           Drying: 100° C., 16 hrs.         Elimina-                                                                            Carbo- 10   41   44    49   46    47  44  49   46                         tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             65   91   89    91   90    90  88  91   90                         materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      32   37   40    37   36    41  40  37   35                         (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         123  102  98    102  106   96  100 102  112                        required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________

EXAMPLE 9

The reactivated catalyst obtained in Example 7 (Catalyst D₄ -13) was treated with a 0.1 N aqueous solution of sodium hydroxide at 100° C. under 1 atm. (absolute) for 3 hours, washed with water at 100° C. for 2 hours and dried at 100° C. for 16 hours. Then, the resulting catalyst was again subjected to treatment with a 0.5% aqueous solution of formaldehyde at 20° C. under 1 atm. (absolute) for 3 hours and treatment with a 0.1 N aqueous solution of sodium hydroxide at 100° C. under 1 atm. (absolute) for 3 hours, followed by washing with water at 100° C. for 2 hours and drying at 100° C. for 16 hours. The thus reactivated catalyst was used for steam-reforming under the same conditions as stated in Example 7. The results are as follows: elimination percentage of poisonous materials: carbonaceous materials, 80 %; sulfurous material, 100%. Specific surface area: 42 m² /g-Ru. Amount of catalyst required for reaction: 92 ml.

As seen from the above results, the repeating treatments with a reducing substance and with an inorganic alkaline substance are quite effective for reactivation of the catalyst.

EXAMPLE 10

The reactivated catalyst obtained in Example 7 (Catalyst D₄ -17) was treated with a 0.375 N aqueous solution of barium hydroxide at 80° C. under 1 atm. (absolute) for 3 hours, washed with water at 100° C. for 2 hours and dried at 100° C. for 16 hours. Then, the resulting catalyst was again subjected to treatment with a 2.0% aqueous solution of sodium formate at 20° C. under 1 atm. (absolute) for 3 hours and treatment with a 0.375 N aqueous solution of barium hydroxide at 80° C. under 1 atm. (absolute) for 3 hours, followed by washing with water at 100° C. for 2 hours and drying at 100° C. for 16 hours. The thus reactivated catalyst was used for steam-reforming under the same conditions as stated in Example 7. The results are as follows: elimination percentage of poisonous materials: carbonaceous materials, 76%; sulfurous material, 100%. Specific surface area: 42 m² /g-Ru. Amount of catalyst required for reaction: 92 ml.

As seen from the above results, the repeating treatments with an inorganic alkaline substance and with a reducing substance are quite effective for reactivation of the catalyst.

EXAMPLE 11

The reactivated catalysts obtained in Example 4 (Catalyst E₃ -5) and in Example 4 (Catalyst E₃ -7) were each reused for steam-reforming under the same conditions as shown in Example 3. The results are shown in Table 6, from which it is understood that the reactivated catalysts show the similar behavior to the fresh catalyst (Catalyst A₂) in depression of the catalytic activity and their catalytic activity, particularly that of Catalyst E₃ -5, is nearly equal to the catalytic activity of the fresh catalyst.

                  TABLE 6                                                          ______________________________________                                         Catalyst            A.sub.2  E.sub.3 -5                                                                              E.sub.3 -7                               ______________________________________                                         Amount of catalyst                                                                         Start        92       95    102                                    required for                                                                   reaction (ml)                                                                              600 hours   164      171    183                                                1200 hours  221      232    250                                    ______________________________________                                    

EXAMPLE 12

The reactivated catalysts obtained in Example 4 (Catalyst E₃ -13) and in Example 6 were each reused for steam-reforming under the same conditions as shown in Example 3. The results are shown in Table 7, from which it is seen that the reactivated catalysts show the similar behavior to the fresh catalyst (Catalyst A₂) in depression of the catalytic activity and their catalytic activity, particularly that of the reactivated catalyst obtained in Example 6 is nearly equal to the catalytic activity of the fresh catalyst.

                  TABLE 7                                                          ______________________________________                                                                            Obtained in                                 Catalyst          A.sub.2  E.sub.3 -13                                                                            Example 6                                   ______________________________________                                         Amount of catalyst                                                                         Start      92      100    93                                       required for                                                                   reaction (ml)                                                                              600 hours 164      179   166                                                   1200 hours                                                                               221      242   224                                       ______________________________________                                    

EXAMPLE 13

The reactivated catalysts obtained in Example 8 (Catalyst E₅ -8) and in Example 9 were each reused for steam-reforming under the same conditions as shown in Example 7. The results are shown in Table 8, from which it is seen that the reactivated catalysts show the similar behavior to the fresh catalyst (Catalyst A₄) in depression of the catalytic activity.

                  TABLE 8                                                          ______________________________________                                                                            Obtained in                                 Catalyst         A.sub.4  E.sub.5 -8                                                                              Example 9                                   ______________________________________                                         Amount of catalyst                                                                         Start     91       95     92                                       required for                                                                   reaction (ml)                                                                              200 hours                                                                               156      167    159                                                   400 hours                                                                               222      238    226                                       ______________________________________                                    

EXAMPLE 14

The reactivated catalysts obtained in Example 8 (Catalyst E₅ -16) and in Example 10 were each reused for steam-reforming under the same conditions as shown in Example 7. The results are shown in Table 9, from which it is seen that the reactivated catalysts show the similar behavior to the fresh catalyst (Catalyst A₄) in depression of the catalytic activity.

                  TABLE 9                                                          ______________________________________                                                                            Obtained in                                 Catalyst         A.sub.4  E.sub.5 -16                                                                             Example 10                                  ______________________________________                                         Amount of catalyst                                                                         Start     91       96     92                                       required for                                                                   reaction (ml)                                                                              200 hours                                                                               156      166    160                                                   400 hours                                                                               222      235    229                                       ______________________________________                                    

EXAMPLE 15

A catalyst comprising 2.0% of ruthenium and 0.1% of chromium oxide deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₁₀ ") (325 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising naphtha (content of sulfur, 2 ppm; final boiling point, 168° C.), steam, hydrogen, methane and carbon oxides was fed therein to effect continuously steam-reforming reaction for 1500 hours under the following conditions:

Temperature of reactor: inlet, 450° C., outlet, 524° C.;

Space velocity: 2000 (1/hr);

Ratio of steam/hydrocarbon: 0.9 (number of oxygen atoms per one carbon atom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 1500 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₁₀ ") was treated under the conditions as shown in Table 10 for reactivation. The reactivated catalyst was reused in steam-reforming reaction under the same conditions as mentioned above. The results are shown in Table 10.

As seen from Table 10, the reactivation treatment with gaseous materials is effective for elimination of carbonaceous materials, but removal of sulfurous materials in insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalysts C₁₀ -1 to C₁₀ -5). In the case of treatment with an inorganic alkaline substance, elimination of sulfurous materials and recovery of the dispersibility (as well as recovery of the catalytic activity) are good.

                                      TABLE 10                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.10                                                                          B.sub.10                                                                          C.sub.10 -1                                                                       C.sub.10 -2                                                                         C.sub.10 -3                                                                         C.sub.10 -4                                                                         C.sub.10 -5                                                                          D.sub.10 -1                                                                        D.sub.10 -2                                                                         D.sub.10 -3                 __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          -- -- H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                  H.sub.2 O:N.sub.2                                                                   O.sub.2 :N.sub.2                                                                    O.sub.2 :H.sub.2 O:                                                                  0.375N                                                                             0.375N                                                                              0.375N                      tions                                                                               agent*          (= 1:1                                                                              (= 3:1                                                                              (= 21:                                                                              N.sub.2 (= 10:                                                                       NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                of                   by mol)                                                                             by mol)                                                                             79 by                                                                               50:40 by                                   treat-                         volume)                                                                             volume)                                    ment                                                                           for  Temper-                                                                               -- -- 600                                                                               600  650  500  600   100 100  100                         reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              -- -- 6.0                                                                               6.0  6.0  6.0  6.0   1.0 1.0  1.0                              (ata)                                                                          Time (hrs)                                                                            -- -- 6.0                                                                               6.0  12.0 5.0  10.0  1.5 3.0  3.0                         Post-treat- -- -- -- --   --   --   --    Water washing: 100° C.,       ment                                      2 hrs.                                                                         Drying: 100° C., 16                                                     hrs.                                 Elimina-                                                                            Carbo- -- -- 78 80   100  100  100   55  54   50                          tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- -- 21 28   32   40   38    95  93   87                          materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43 20 19 19   19   17   18    35  36   33                          (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         52.5                                                                              -- -- --   --   --   --    63  64   66                          required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________      Note:                                                                          *In case of Catalysts C.sub.10 -1 to C.sub.10 -5, the treatment was            carried out with a space velocity of 2500.sup.10 (1 hr).                 

    Reactivated                                                                                                        Catalyst    D.sub.10 -4                                                                        D.sub.10 -5                __________________________________________________________________________                                         Condi-                                                                               Reactivating                                                                         0.375N                                                                             0.375N                                                         tions                                                                               agent  NaOH                                                                               NaOH                                                           of                                                                             treat-                                                                         ment                                                                           for  Temper-                                                                               50  30                                                             reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0                                                                 (ata)                                                                          Time (hrs)                                                                            6.0 10.0                                                                Post-treat-                                                                           Water washing:                                                                 100° C.,                                                         ment   2 hrs.                                                                         Drying: 100° C.,                                                        16 hrs.                                                            Elimina-                                                                            Carbo- 41  40                                                             tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             78  75                                                             materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      28  28                                                             (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         85  --                                                             required for reac-                                                             tion (ml)                                  __________________________________________________________________________

EXAMPLE 16

The reactivated catalysts as obtained in Example 15 (Catalysts C₁₀ -1, C₁₀ -2 and C₁₀ -5) were each subjected to further treatment for reactivation under the conditions as shown in Table 11. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 15. The results are shown in Table 11.

As seen from Table 11, the catalysts (E₁₁ -1 to E₁₁ -6) reactivated in two steps are much recovered in catalytic activity.

                                      TABLE 11                                     __________________________________________________________________________     Catalyst    E.sub.11 -1                                                                        E.sub.11 -2                                                                        E.sub.11 -3                                                                         E.sub.11 -4                                                                         E.sub.11 -5                                                                        E.sub.11 -6                                                                        E.sub.11 -7                                                                        E.sub.11 -8                          Catalyst used                                                                              C.sub.10 -1                                                                        C.sub.10 -1                                                                        C.sub.10 -1                                                                         C.sub.10 -1                                                                         C.sub.10 -2                                                                        C.sub.10 -5                                                                        C.sub.10 -1                                                                        C.sub.10 -1                          __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                                                                              0.1N                                                                               0.375N                                                                             0.375N                                                                             0.375N                               tions                                                                               agent  NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                 of                                                                             treat-                                                                         ment                                                                           for  Temper-                                                                               50  80  100  100  100 80  30  30                                   reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0 1.0  1.0  1.0 1.0 1.0 1.0                                       (ata)                                                                          Time (hrs)                                                                            3.0 1.5 1.5  2.0  1.5 1.5 10.0                                                                               3.0                                  Post-treat- Water washing: 100° C., 2 hrs.                              ment        Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 81  86  85   83   83  100 80  80                                   tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurus                                                                              83  96  94   88   90  97  80  48                                   materials                                                                           materials                                                                 (%)                                                                             Specific surface area                                                                     31  38  37   35   37  38  28  23                                   (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         78  58  61   63   61  58  --  --                                   required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________

EXAMPLE 17

The reactivated catalysts as obtained in Example 16 (Catalysts E₁₁ -1, E₁₁ -7 and E₁₁ -8) were each subjected to further treatment for reactivation under the conditions as shown in Table 12. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 15. The results are shown in Table 12.

As seen from Table 12, the catalysts (F₁₂ -1 to F₁₂ -11) reactivated in three steps are much recovered in catalytic activity.

                                      TABLE 12                                     __________________________________________________________________________     Catalyst    F.sub.12 -1                                                                        F.sub.12 -2                                                                         F.sub.12 -3                                                                         F.sub.12 -4                                                                          F.sub.12 -5                                                                        F.sub.12 -6                                                                        F.sub.12 -7                                                                         F.sub.12 -8                                                                         F.sub.12 -9                                                                        F.sub.12 -10                                                                        F.sub.12 -11        Catalyst used                                                                              E.sub.11 -1                                                                        E.sub.11 -1                                                                         E.sub.11 -1                                                                         E.sub.11 -1                                                                          E.sub.11 -1                                                                        E.sub.11 -7                                                                        E.sub.11 -7                                                                         E.sub.11 -7                                                                         E.sub.11 -7                                                                        E.sub.11 -7                                                                         E.sub.11            __________________________________________________________________________                                                                -8                  Condi-                                                                              Reactivating                                                                          0.4%                                                                               0.5% 0.3% 0.3%  0.3%                                                                               0.4%                                                                               0.5% 0.3% 0.7%                                                                               2.0% 1.0%                tions                                                                               agent  Hydra-                                                                             Formal-                                                                             Sodium                                                                              Lithium                                                                              Glu-                                                                               Hydra-                                                                             Formal-                                                                             Sodium                                                                              Sodium                                                                             Sodium                                                                              Hydra-              of          zine                                                                               dehyde                                                                              boro-                                                                               aluminum                                                                             cose                                                                               zine                                                                               dehyde                                                                              boro-                                                                               tart-                                                                              formate                                                                             zine                treat-               hydride                                                                             hydride            hydride                                                                             rate                         ment                                                                           for  Temper-                                                                               20  20   20   20    20  20  20   20   20  20   60                  reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0  1.0  1.0   1.0 1.0 1.0  1.0  1.0 1.0  1.0                      (ata)                                                                          Time (hrs)                                                                            3.0 3.0  3.0  3.0   3.0 3.0 3.0  3.0  3.0 3.0  3.0                 Post-treat-  Water washing: 75° C., 3 hrs.                              ment        Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 81  81   81   81    81  80  80   80   80  80   80                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             96  90   95   92    92  92  87   90   91  93   94                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      41  40   40   40    40  37  36   35   36  36   39                  (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         53  55   56   53    56  60  61   63   61  61   56                  required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________

EXAMPLE 18

The reactivated catalysts obtained in Example 16 (Catalyst E₁₁ -2) and in Example 17 (Catalyst F₁₂ -1) were each reused for steam-reforming under the same conditions as shown in Example 15. The results are shown in Table 13, from which it is seen that the reactivated catalysts show the similar behavior to the fresh catalyst (Catalyst A₁₀) in depression of the catalytic activity and their catalytic activity, particularly that of Catalyst F₁₂ -1 is nearly equal to the catalytic activity of the fresh catalyst.

                  TABLE 13                                                         ______________________________________                                         Catalyst             A.sub.10                                                                               E.sub.11 -2                                                                            F.sub.12 -1                               ______________________________________                                         Amount of catalyst                                                                           Start      52.5    58    53                                      required for                                                                   reaction (ml) 300 hours  123.5   139.5 125                                                   600 hours  183     208.5 186                                                   900 hours  252     289   257                                     ______________________________________                                    

EXAMPLE 19

A catalyst comprising 2.6% of ruthenium and 0.1% of chromium oxide deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₁₄ ") (325 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising naphtha (content of sulfur, 2 ppm; final boiling point, 168° C.), steam, hydrogen, methane and carbon oxides was fed therein to effect continuously steam-reforming reaction for 2400 hours under the following conditions:

Temperature of reactor: inlet, 400° C., outlet, 517° C.;

Space velocity: 1500 (1/hr);

Ratio of steam/hydrocarbon: 0.7 (number of oxygen atoms per one carbon atom in the feeding gaseous mixture);

Pressure: 13 atm. (absolute)

After 2400 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₁₄ ") was treated under the conditions as shown in Table 14 for reactivation. The reactivated catalyst was reused in steam-reforming reaction under the same conditions as mentioned above. The results are shown in Table 14.

As seen from Table 14, the reactivation treatment with gaseous materials is effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalysts C₁₄ -1 to C₁₄ -5). In the case of treatment with an inorganic alkaline substance, elimination of sulfurous materials and recovery of the dispersibility (as well as recovery of the catalytic activity) are good.

                                      TABLE 14                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.14                                                                          B.sub.14                                                                          C.sub.14 -1                                                                       C.sub.14 -2                                                                         C.sub.14 -3                                                                         C.sub.14 -4                                                                        C.sub.14 -5                                                                          D.sub.14 -1                                                                        D.sub.14 -2                                                                        D.sub.14 -3                   __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          -- -- H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                  H.sub.2 O:N.sub.2                                                                   O.sub.2 :N.sub.2                                                                   O.sub.2 :H.sub.2 O:                                                                  0.375N                                                                             0.375N                                                                             0.375N                        tions                                                                               agent*          (= 1:1                                                                              (= 3:1                                                                              (= 21:                                                                             N.sub.2 (= 10:                                                                       NaOH                                                                               NaOH                                                                               NaOH                          of                   by mol)                                                                             by mol)                                                                             79 by                                                                              50:40 by                                    treat-                         volume)                                                                            volume)                                     ment                                                                           for  Temper-                                                                               -- -- 600                                                                               600  650  500 600   30  30  50                            reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              -- -- 6.0                                                                               6.0  6.0  6.0 6.0   1.0 1.0 1.0                                (ata)                                                                          Time (hrs.)                                                                           -- -- 6.0                                                                               6.0  12.0 5.0 10.0  3.0 10.0                                                                               6.0                           Post-treat- -- -- -- --    --  --  --    Water washing: 100° C.,        ment                                     2 hrs.                                                                         Drying: 100° C., 16 hrs.       Elimina-                                                                            Carbo- -- -- 75 78   100  100 100   12  41  43                            tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- -- 19 25   30   37  35    32  72  78                            materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43 20 19 19   19   17  18    21  27  28                            (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         92 -- -- --   --   --  --    --  --  147                           required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________      Note:                                                                          *In case of Catalysts C.sub.14 -1 to C.sub.14 -5, the treatment was            carried out with a space velocity of 2500.sup.14 (1/hr).                 

    Reactivated                                                                                   Catalyst    D.sub.14 -4                                                                        D.sub.14 -5                                                                        D.sub.14 -6                                                                         D.sub.14 -7                                                                        D.sub.14 -8                                                                        D.sub.14 -9                    __________________________________________________________________________                    Condi-                                                                              Reactivating                                                                          0.375N                                                                             0.375N                                                                             0.375N                                                                              0.1N                                                                               0.375N                                                                             0.375N                                        tions                                                                               agent  NaOH                                                                               Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                                                        NaOH                                                                               Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                                  of                                                                             treat-                                                                         ment                                                                           for  Temper-                                                                               100 100 100  100 80  100                                           reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0 1.0  1.0 1.0 1.0                                                (ata)                                                                          Time (hrs)                                                                            3.0 3.0 3.0  3.0 3.0 1.5                                                Post-treat-                                                                           Water washing: 100° C., 2 hrs.                                   ment   Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 52  51  47   40  44  45                                            tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             90  88  82   75  77  76                                            materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      34  34  32   30  30  29                                            (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         110 112 116  120 122 127                                           required for reac-                                                             tion (ml)                                                       __________________________________________________________________________

EXAMPLE 20

The reactivated catalysts as obtained in Example 19 (Catalysts D₁₄ -7 to D₁₄ -9)were each subjected to further treatment for reactivation under the conditions as shown in Table 15. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 19. The results are shown in Table 15.

As seen from Table 15, the catalysts (E₁₅ -1 to E₁₅ -5) reactivated in two steps are much recovered in catalytic activity.

                                      TABLE 15                                     __________________________________________________________________________     Catalyst    E.sub.15 -1                                                                         E.sub.15 -2                                                                          E.sub.15 -3                                                                          E.sub.15 -4                                                                         E.sub.15 -5                                  Catalyst used                                                                              D.sub.14 -7                                                                         D.sub.14 -7                                                                          D.sub.14 -7                                                                          D.sub.14 -8                                                                         D.sub.14 -9                                  __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          H.sub.2                                                                             H.sub.2 :H.sub.2 O                                                                   O.sub.2 :H.sub.2 O:                                                                  H.sub.2                                                                             H.sub.2 :H.sub.2 O                           tions                                                                               agent*      (= 1:1                                                                               N.sub.2 (= 10:                                                                            (= 1:1                                       of               by mol)                                                                              50:40 by   by mol)                                      treat-                 volume)                                                 ment                                                                           for  Temper-                                                                               600  600   600   650  650                                          reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              6.0  6.0   6.0   6.0  6.0                                               (ata)                                                                          Time (hrs)                                                                            6.0  6.0   10.0  12.0 12.0                                              Post-treat-                                                                           --   --    --    --   --                                                ment                                                                      Elimina-                                                                            Carbo- 85   87    100   100  100                                          tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             80   81    84    81   82                                           materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      31   31    30    30   30                                           (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         105  105   110   110  112                                          required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________      Note:                                                                          *In case of Catalysts E.sub.15 -1 to E.sub.15 -5, the treatment was            carried out with a space velocity of 2500 (1/hr).                        

EXAMPLE 21

The reactivated catalysts as obtained in Example 19 (Catalysts D₁₄ -1 to D₁₄ -4, D₁₄ -8 and D₁₄ -9) were each subjected to further treatment for reactivation under the conditions as shown in Table 16. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 19. The results are shown in Table 16.

As seen from Table 16, the catalysts (E₁₆ -1 to E₁₆ -10) reactivated in two steps are much recovered in catalytic activity.

                                      TABLE 16                                     __________________________________________________________________________     Catalyst    E.sub.16 -1                                                                        E.sub.16 -2                                                                        E.sub.16 -3                                                                         E.sub.16 -4                                                                        E.sub.16 -5                                                                         E.sub.16 -6                                                                         E.sub.16 -7                                                                         E.sub.16 -8                                                                        E.sub.16 -9                                                                        E.sub.16 -10               Catalyst used                                                                              D.sub.14 -1                                                                        D.sub.14 -2                                                                        D.sub.14 -3                                                                         D.sub.14 -3                                                                        D.sub.14 -3                                                                         D.sub.14 -4                                                                         D.sub.14 -8                                                                         D.sub.14 -8                                                                        D.sub.14 -9                                                                        D.sub.14 -9                __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          1.0%                                                                               0.4%                                                                               0.3% 0.5%                                                                               0.3% 0.3% 0.5% 0.7%                                                                               0.4%                                                                               2.0%                       tions                                                                               agent  Hydra-                                                                             Hydra-                                                                             Lithium                                                                             Formal-                                                                            Sodium                                                                              Glucose                                                                             Formal-                                                                             Sodium                                                                             Hydra-                                                                             Sodium                     of          zine                                                                               zine                                                                               aluminum                                                                            dehyde                                                                             boro-     dehyde                                                                              tart-                                                                              zine                                                                               formate                    treat-              hydride  hydride        rate                               ment                                                                           for  Temper-                                                                               60  20  20   20  20   20   20   20  20  20                         reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              1.0 1.0 1.0  1.0 1.0  1.0  1.0  1.0 1.0 1.0                             (ata)                                                                          Time (hrs)                                                                            3.0 3.0 3.0  3.0 3.0  3.0  3.0  3.0 3.0 3.0                        Post-treat- Water washing: 75° C., 3 hrs.                               ment        Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 12  41  43   43  43   52   44   44  45  45                         tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             89  91  93   93  93   97   90   88  92  90                         materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      34  36  36   36  34   40   36   36  36  36                         (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         108 110 102  106 108  95   106  106 102 102                        required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________

EXAMPLE 22

The reactivated catalysts as obtained in Example 21 (Catalysts E₁₆ -1, E₁₆ -3 and E₁₆ -5 to E₁₆ -7) were each subjected to further treatment for reactivation under the conditions as shown in Table 17. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 15. The results are shown in Table 17.

As seen from Table 17, the catalysts (F₁₇ -1 to F₁₇ -5) reactivated in three steps are much recovered in catalytic activity.

                                      TABLE 17                                     __________________________________________________________________________     Catalyst    F.sub.17 -1                                                                        F.sub.17 -2                                                                        F.sub.17 -3                                                                         F.sub.17 -4                                                                         F.sub.17 -5                                      Catalyst used                                                                              E.sub.16 -1                                                                        E.sub.16 -3                                                                        E.sub.16 -5                                                                         E.sub.16 -6                                                                         E.sub.16 -7                                      __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          H.sub.2                                                                            H.sub.2                                                                            H.sub.2 :H.sub.2 O                                                                  H.sub.2 O:N.sub.2                                                                   O.sub.2 :H.sub.2 O:N.sub.2                       tions                                                                               agent*)        ( = 1:1                                                                             ( = 3:1                                                                             ( = 10:50:40                                     of                  by mol)                                                                             by mol)                                                                             by volume)                                       treat-                                                                         ment                                                                           for  Temper-                                                                               650 600 600  650  600                                              reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              6.0 6.0 6.0  6.0  6.0                                                   (ata)                                                                          Time (hrs)                                                                            12.0                                                                               6.0 6.0  12.0 10.0                                                  Post-treat-                                                                           --  --  --   --   --                                                    ment                                                                      Elimina-                                                                            Carbo- 100 86  87   100  100                                              tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             96  96  96   97   94                                               materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      35  37  35   40   37                                               (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         100 96  102  93   98                                               required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________      Note:                                                                          *In case of Catalysts F.sub.17 -1 to F.sub.17 -5, the treatment was            carried out with space velocity of 2500 (1/hr).                          

EXAMPLE 23

The reactivated catalysts obtained in Example 20 (Catalyst E₁₅ -1) and in Example 22 (Catalyst F₁₇ -4) were each reused for steam-reforming under the same conditions as shown in Example 19. The results are shown in Table 18, from which it is seen that the reactivated catalysts show the similar behavior to the fresh catalyst (Catalyst A₁₄) in depression of the catalytic activity and their catalytic activity, particularly that of Catalyst F₁₇ -4, is nearly equal to the catalytic activity of the fresh catalyst.

                  TABLE 18                                                         ______________________________________                                         Catalyst             A.sub.14                                                                               E.sub.15 -1                                                                            F.sub.17 -4                               ______________________________________                                         Amount of catalyst                                                                           Start       92     105    93                                     required for  600 hours  164     191   168                                     reaction (ml) 1200 hours 221     260   227                                     ______________________________________                                    

EXAMPLE 24

A catalyst comprising 2% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter (hereinafter referred to as "Catalyst A₁₈ ") (6700 ml) was charged into a tubular reactor of 5 inch in diameter, and methanol and steam were fed therein to effect continuously steam-reforming reaction for 2000 hours under the following conditions:

Temperature of reactor: inlet, 580° C., outlet, 620° C.;

Space velocity: 15800 (1/hr);

Ratio of steam/methanol: 1.5 (by mol);

Pressure: 6 atm. (absolute)

After 2000 hours, the catalyst (hereinafter referred to as "Catalyst B₁₈ ") was treated under the same conditions as shown in Table 18 for reactivation. The reactivated catalyst was reused in steam-reforming reaction under the same conditions as mentioned above. The results are shown in Table 18.

As seen from Table 18, treatment with an inorganic alkaline substance or a reducing substance shows recovery of the catalytic activity.

                                      TABLE 18                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.18                                                                          B.sub.18                                                                          D.sub.18 -1                                                                         D.sub.18 -2                                                                          D.sub.18 -3                                                                         D.sub.18 -4                                  __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          -- -- 0.375N                                                                              0.375N                                                                               1.0% 0.3%                                         tions                                                                               agent        NaOH NaOH  Hydra-                                                                              Glucose                                      of                           zine                                              treat-                                                                         ment                                                                           for  Temper-                                                                               -- -- 30   100   60   20                                           reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              -- -- 1.0  1.0   1.0  1.0                                               (ata)                                                                          Time (hrs)                                                                            -- -- 3.0  3.0   3.0  3.0                                          Post-treat- -- -- Water washing:                                                                            Water washing:                                    ment              100° C., 2 hrs.                                                                    75° C., 3 hrs.                                               Drying: 100° C., 16 hrs.                                                           Drying: 100° C., 16 hrs.                   Elimina-                                                                            Carbo- -- -- 12   53    0    0                                            tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- -- --   --    --   --                                           materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43 17 20   34    23    23                                          (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         1.3                                                                               -- --   1.6   3.8  4.0                                          required for reac-                                                             tion (1)                                                                       __________________________________________________________________________

EXAMPLE 25

The reactivated catalysts as obtained in Example 24 (Catalysts D₁₈ -1 to D₁₈ -4) were each subjected to further treatment for reactivation under the conditions as shown in Table 19. The thus reactivated catalysts were each reused for continuous steam-reforming under the same conditions as shown in Example 24. The results are shown in Table 19.

As seen from Table 19, the catalysts (E₁₉ -1 to E₁₉ -4) reactivated in two steps are much more recovered in catalytic activity than the catalysts (D₁₈ -1 to D₁₈ -4) reactivated in one step.

                  TABLE 19                                                         ______________________________________                                         Catalyst      E.sub.19 -1                                                                            E.sub.19 -2                                                                             E.sub.19 -3                                                                           E.sub.19 -4                              Cataylst used D.sub.18 -1                                                                            D.sub.18 -2                                                                             D.sub.18 -3                                                                           D.sub.18 -4                              ______________________________________                                         Condi- Reactivating                                                                              1.0%    0.3%   0.375N 0.375N                                 tions  agent      Hydra-  Sodium NaOH   NaOH                                   of                zine    boro-                                                treat-                    hydride                                              ment                                                                           for    Temper-    60      20     100    80                                     reacti-                                                                               ature (°C.)                                                      vation                                                                                Pressure   1.0     1.0    1.0    1.0                                           (ata)                                                                          Time (hrs) 3.0     3.0    3.0    3.0                                    Post-treat-   Water washing:                                                                              Water washing:                                      ment          75° C., 3 hrs.                                                                       100° C., 2 hrs.                                            Drying: 100° C.,                                                                     Drying: 100° C.,                                           16 hrs.      16 hrs.                                             Elimina-                                                                              Carbo-     12      52     52     50                                     tion per-                                                                             naceous                                                                 centage                                                                               materials                                                               of                                                                             poisonous                                                                             Sulfurous   --      --     --     --                                    materials                                                                             materials                                                               (%)                                                                            Specific surface area                                                                        34      40       41     38                                       (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                           1.5     1.4      1.3    1.4                                      required for reac-                                                             tion (1)                                                                       ______________________________________                                    

EXAMPLE 26

A catalyst comprising 2.0% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₂₀ ") (290 ml) was charged into a tubular reactor of 1 inch in diameter, and methane (content of sulfur, 2 ppm) and air were fed therein to effect continuously partial oxidation for 2500 hours under the following conditions:

Temperature of reactor: inlet, 310° C., outlet, 700° C.;

Space velocity: 17500 (1/hr);

Ratio of air/methane: 2.37 (by mol);

Pressure: 1 atm. (absolute)

After 2500 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₂₀ ") was treated under the conditions as shown in Table 20 for reactivation. The reactivated catalyst was reused in partial oxidation under the same conditions as mentioned above. The results are shown in Table 20.

As seen from Table 20, treatment with an inorganic alkaline substance or a reducing substance shows recovery of the catalytic activity.

                                      TABLE 20                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.20                                                                          B.sub.20                                                                          D.sub.20 -1                                                                          D.sub.20 -2                                                                          D.sub.20 -3                                                                          D.sub.20 -4                                __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          -- -- 0.375N                                                                               0.375N                                                                               1.0%  2.0%                                       tions                                                                               agent        NaOH  NaOH  Formal-                                                                              Sodium                                     of                            dehyde                                                                               formate                                    treat-                                                                         ment                                                                           for  Temper-                                                                               -- -- 30    100   60    20                                         reacti-                                                                             ature (°C.)                                                        vation                                                                              Pressure                                                                              -- -- 1.0   1.0   1.0   1.0                                             (ata)                                                                          Time (hrs)                                                                            -- -- 3.0   3.0   3.0   3.0                                        Post-treat- -- -- Water washing: 100° C.,                                                             Water washing: 75° C.,                    ment              2 hrs.      3 hrs.                                                             Drying: 100° C., 16 hrs.                                                            Drying: 100° C., 16 hrs.                  Elimina-                                                                            Carbo- -- -- 12    52    0     0                                          tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- -- 32    95    70    55                                         materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43 17 21    33    21    21                                         (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         58 -- --    67    170   172                                        required for reac-                                                             tion (ml)                                                                      __________________________________________________________________________

EXAMPLE 27

The reactivated catalysts as obtained in Example 26 (Catalysts D₂₀ -1 to D₂₀ -4) were each subjected to further treatment for reactivation under the conditions as shown in Table 21. The thus reactivated catalysts were each reused for continuous partial oxidation under the same conditions as shown in Example 26. The results are shown in Table 21.

As seen from Table 21, the catalysts (E₂₁ -1 to E₂₁ -4) reactivated in two steps are much more recovered in catalytic activity than the catalysts (D₂₀ -1 to D₂₀ -4) reactivated in one step.

                  TABLE 21                                                         ______________________________________                                         Catalyst      E.sub.21 -1                                                                            E.sub.21 -2                                                                             E.sub.21 -3                                                                           E.sub.21 -4                              Catalyst used D.sub.20 -1                                                                            D.sub.20 -1                                                                             D.sub.20 -3                                                                           D.sub.20 -4                              ______________________________________                                         Condi- Reactivating                                                                              1.0%    0.3%   0.375N 0.375N                                 tions  agent      Hydra-  Sodium NaOH   NaOH                                   of                zine    boro-                                                treat-                    hydride                                              ment                                                                           for    Temper-    60      20     80     80                                     reacti-                                                                               ature (°C.)                                                      vation                                                                                Pressure   1.0     1.0    1.0    1.0                                           (ata)                                                                          Time (hrs) 3.0     3.0    3.0    3.0                                    Post-treat-   Water washing:                                                                              Water washing:                                      ment          75° C., 3 hrs.                                                                       100° C., 2 hrs.                                            Drying: 100° C.,                                                                     Drying: 100° C.,                                           16 hrs.      16 hrs.                                             Elimina-                                                                              Carbo-     12      52     47     47                                     tion per-                                                                             naceous                                                                 centage                                                                               materials                                                               of                                                                             poisonous                                                                             Sulfurous  95      97     92     93                                     materials                                                                             materials                                                               (%)                                                                            Specific surface area                                                                        34      40       39     37                                       (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                           68      62       60     62                                       required for reac-                                                             tion (ml)                                                                      ______________________________________                                    

EXAMPLE 28

A catalyst comprising 1.0% of ruthenium and 0.1% of chromium oxide deposited on spheoidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₂₃ ") (400 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising naphtha (content of sulfur, 2 ppm; final boiling point, 108° C.) and hydrogen was fed therein to effect continuously hydro-cracking for 700 hours under the conditions as shown in Table 22:

                  TABLE 22                                                         ______________________________________                                         Temperature of      265° C.                                             reactor at inlet                                                               Pressure            46 atm. (absolute)                                         Ratio of hydrogen/  1.20 (by mol)                                              hydrocarbon                                                                    Mass velocity       500 kg-mol/m.sup.2 . hr                                    ______________________________________                                    

After 700 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₂₃ ") was treated under the conditions as shown in Table 23 for reactivation. The reactivated catalyst was reused in hydro-cracking under the same conditions as mentioned above. The results are shown in Table 23.

As seen from Table 23, the reactivation treatment with hydrogen is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalyst C₂₃). In the case of treatment with an inorganic alkaline substance at room temperature for a long time, elimination of sulfurous materials and recovery of the dispersibility are good, but recovery of the catalytic activity is still not good (Catalysts D₂₃ -1 and D₂₃ -2). When treated with an inorganic alkaline substance under heating, recovery of the catalytic activity is good (Catalysts D₂₃ -3, D₂₃ -4, D₂₃ -5, D₂₃ -14, D₂₃ -15, D₂₃ -16). On the other hand, sole treatment with an aqueous solution of hydrazine is effective in removal of sulfurous materials but almost ineffective in removal of carbonaceous materials. Nevertheless, a tendency to recovery of the catalytic activity is seen (Catalysts D₂₃ -6 to D₂₃ -13).

                                      TABLE 23                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.23                                                                          B.sub.23                                                                          C.sub.23                                                                          D.sub.23 -1                                                                        D.sub.23 -2                                                                        D.sub.23 -3                                                                        D.sub.23 -4                                                                        D.sub.23 -5                                                                        D.sub.23 -6                                                                        D.sub.23 -7                                                                         D.sub.23 -8                  __________________________________________________________________________     Condi-                                                                              Reactivating    0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.4%                                                                               0.3% 0.7%                         tions                                                                               agent*)                                                                               -- -- H.sub.2                                                                           NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               Hydra-                                                                             Lithium                                                                             Sodium                       of                                       zine                                                                               alumi-                                                                              tart-                        treat-                                       num hy-                                                                             rate                         ment                                         dride                             for  Temperature                                                                           -- -- 650                                                                               30  30  50  100 148 20  20   20                           reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              -- -- 6.0                                                                               1.0 1.0 1.0 1.0 5.0 1.0 1.0  1.0                               (ata)                                                                          Time (hrs)                                                                            -- -- 12.0                                                                              3.0 10.0                                                                               6.0 3.0 1.0 3.0 3.0  3.0                          Post-treat- -- --  --                                                                               Water washing: 100° C., 2 hrs.                                                          Water washing: 75° C., 3                                                hrs.                                      ment                 Drying: 100° C., 16 hrs.                                                                Drying: 100° C., 16 hrs.           Elimina-                                                                            Carbo- -- -- 100                                                                               10  30  35  47  50  0   0    0                            tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- -- 20 40  73  79  90  100 70  51   51                           materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43 25 25 27  28  31  36  36  28  29   29                           (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     88 5  5  7   8   50  68  69  40  39   39                           (%)                                                                                        Reactivated                                                        Catalyst    D.sub.23 -9                                                                        D.sub.23 -10                                                                       D.sub.23 -11                                                                       D.sub.23 -12                                                                       D.sub.23 -13                                                                       D.sub.23 -14                                                                       D.sub.23 -15                                                                       D.sub.23 -16                           __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          2.0%                                                                               0.3%                                                                               1.0%                                                                               1.0%                                                                               1.0%                                                                               5.0N                                                                               0.375N                                                                             0.375N                                 tions                                                                               agent*)                                                                               Sodium                                                                             Glu-                                                                               Hydra-                                                                             Form                                                                               Sodium                                                                             NaOH                                                                               Na.sub.2 CO.sub.3                                                                  Ba(OH).sub.2                           of          for-                                                                               cose                                                                               zine                                                                               alde-                                                                              borohy-                                            treat-      mate        hyde                                                                               dride                                              ment                                                                           for  Temperature                                                                           20  20  60  60  60  100 100 100                                    reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0                                         (ata)                                                                          Time (hrs)                                                                            3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0                                    Post-treat- Water washing: 75° C., 3 hrs.                                                               Water washing: 100° C.,                 ment        Drying: 100° C., 16 hrs.                                                                    2 hrs.                                                                         Drying: 100° C., 16 hrs.                Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                                0   0   0   0   0  50  43  40                                     centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             54  51  91  69  88  95  86  82                                     (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                            29  29  29  29  29  38  36  32                                     Conversion of hydrogen                                                                     39  38  45  39  38  70  68  65                                     (%)                                                                            __________________________________________________________________________

EXAMPLE 29

The reactivated catalysts as obtained in Example 28 (Catalysts D₂₃ -1 to D₂₃ -12) were each subjected to further treatment for reactivation under the conditions as shown in Table 24. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Example 28. The results are shown in Table 24.

As seen from Table 24, the catalysts (E₂₄ -1 to E₂₄ -20) reactivated in two steps are much more recovered in catalytic activity than the catalysts (D₂₃ -1 to D₂₃ -12) reactivated in one step.

                                      TABLE 24                                     __________________________________________________________________________     Catalyst    E.sub.24 -1                                                                          E.sub.24 -2                                                                          E.sub.24 -3                                                                        E.sub.24 -4                                                                        E.sub.24 -5                                                                         E.sub.24 -6                                                                         E.sub.24 -7                                                                        E.sub.24 -8                                                                        E.sub.24 -9                                                                        E.sub.24 -10             Catalyst used                                                                              D.sub.23 -1                                                                          D.sub.23 -2                                                                          D.sub.23 -3                                                                        D.sub.23 -3                                                                        D.sub.23 -4                                                                         D.sub.23 -4                                                                         D.sub.23 -6                                                                        D.sub.23 -6                                                                        D.sub.23 -11                                                                       D.sub.23 -12             __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          1.0%  0.4%  0.4%                                                                               0.5%                                                                               0.4% 0.3% 0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                   tions                                                                               agent  Hydra-                                                                               Hydra-                                                                               Hydra-                                                                             Form-                                                                              Hydra-                                                                              Sodium                                                                              NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                     of          zine  zine  zine                                                                               alde-                                                                              zine boro-                                     treat-                      hyde     hydride                                   ment                                                                           for  Temperature                                                                           60    20    20  20  20   20   50  100 100 100                      reacti-                                                                             (°C.) -vation                                                           Pressure                                                                              1.0   1.0   1.0 1.0 1.0  1.0  1.0 1.0 1.0 1.0                           (ata)                                                                          Time (hrs)                                                                            3.0   3.0   3.0 3.0 3.0  3.0  6.0 3.0 3.0 3.0                      Post-treat- Water washing: 75° C., 3 hrs.                                                                         Water washing: 100° C.,                                                 2 hrs.                               ment        Drying: 100° C., 16 hrs.                                                                              Drying: 100° C., 16                                                     hrs.                                 Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               10    30    35  35  47   47   35  49  48  39                       centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             91    93    95  95  98   97   93  98  97  91                       (%)                                                                            Specific surface area                                                                      36    38    38  38  40   40   37  40  42  40                       (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     48    51    74  70  80   77   74  80  81  80                       (%)                                                                            Catalyst    E.sub.24 -11                                                                         E.sub.24 -12                                                                         E.sub.24 13                                                                        E.sub.24 -14                                                                       E.sub.24 -15                                                                         E.sub.24 -16                                                                       E.sub.24 -17                                                                       E.sub.24 -18                                                                       E.sub.24 -19                                                                       E.sub.24 -20             Catalyst used                                                                              D.sub.23 -1                                                                          D.sub.23 -2                                                                          D.sub.23 -3                                                                        D.sub.23 -3                                                                        D.sub.23 -4                                                                          D.sub.23 -4                                                                        D.sub.23 -7                                                                        D.sub.23 -8                                                                        D.sub. -9                                                                          D.sub.23 -10             __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          0.3%  0.3%  0.7%                                                                               2.0%                                                                               0.3%  0.3%                                                                               0.375N                                                                             0.1N                                                                               0.375N                                                                             0.375                    tions                                                                               agent  Lithium                                                                              Lithium                                                                              Sodium                                                                             Sodium                                                                             Lithium                                                                              Glu-                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                     of          aluminum                                                                             aluminum                                                                             tart-                                                                              for-                                                                               aluminum                                                                             cose                                     treat-      hydride                                                                              hydride                                                                              rate                                                                               mate                                                                               hydride                                        ment                                                                           for  Temperature                                                               reacti-                                                                             (°C.)                                                                          20    20    20  20  20    20  50  100 100 80                       vation                                                                              Pressure                                                                       (ata)  1.0   1.0   1.0 1.0 1.0   1.0 1.0 1.0 1.0 1.0                           Time (hrs)                                                                            3.0   3.0   3.0 3.0 3.0   3.0 6.0 3.0 1.5 3.0                      Post-treat- Water washing: 75° C., 3 hrs.                                                                         Water washing: 100° C.,                                                 2 hrs.                               ment        Drying: 100° C., 16 hrs.                                                                              Drying: 100° C., 16                                                     hrs.                                 Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               10    30    35  35  47    47  35  36  38  39                       centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             68    88    91  92  97    97  91  90  95  94                       (%)                                                                            Specific surface area                                                                      36    38    39  39  42    41  39  39  39  39                       (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     50    50    74  74  81    80  77  74  74  74                       (%)                                                                            __________________________________________________________________________

EXAMPLE 30

The reactivated catalyst obtained in Example 28 (Catalyst D₂₃ -3) was treated with a 0.4% aqueous solution of hydrazine at 20° C. under 1 atm. (absolute) for 3 hours, washed with water at 75° C. for 3 hours and dried at 100° C. for 16 hours. Then, the resulting catalyst was again subjected to treatment with a 0.375 N aqueous solution of sodium hydroxide at 50° C. under 1 atm. (absolute) for 6 hours and treatment with a 0.4% aqueous solution of hydrazine at 20° C. under 1 atm. (absolute) for 3 hours, followed by washing with water at 75° C. for 3 hours and drying at 100° C. for 16 hours. The thus reactivated catalyst was used for hydro-cracking under the same conditions as shown in Table 22. The results are shown in Table 25.

                  TABLE 25                                                         ______________________________________                                         Catalyst                   F                                                   ______________________________________                                         Elimination per-    Carbon-                                                    centage of          aceous     70                                              poisonous           materials                                                  materials           Sulfurous  100                                             (%)                 materials                                                  Specific surface area          42                                              (m.sup.2 /g-Ru)                                                                Conversion of hydrogen (%)     81                                              ______________________________________                                    

As seen from the above results, the repeating treatments with an inorganic alkaline substance and with a reducing substance are quite effective for reactivation of the catalyst.

EXAMPLE 31

The reactivated catalysts obtained in Example 29 (Catalysts E₂₄ -5 and E₂₄ -7) were used for continuous hydro-cracking under the conditions as shown in Example 28. The reactivated catalysts showed a similar tendency to a freshly prepared catalyst (Catalyst A₂₃) in depression of the catalytic activity.

EXAMPLE 22

A catalyst comprising 0.3% of ruthenium and 0.1% of chromium oxide deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₂₈ ") (1000 ml) was charged into a tubular reactor of 1 inch in diameter, and naphtha (content of sulfur, 2 ppm; final boiling point, 108° C.) and hydrogen were fed therein to effect continuously hydrocracking reaction under the conditions as shown in Table 27.

                  TABLE 27                                                         ______________________________________                                         Temperature of      265° C.                                             reactor at inlet                                                               Pressure            46 atm. (absolute)                                         Ratio of hydrogen/  1.20 (by mol)                                              hydrocarbon                                                                    Mass velocity       500 kg-mol/m.sup.2 . hr                                    ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₂₈ ") was treated under the conditions as shown in Table 28 for reactivation. The reactivated catalyst was reused in hydro-cracking reaction under the same conditions as mentioned above. The results are shown in Table 28.

As seen from Table 28, the reactivation treatment was gaseous materials such as hydrogen, hydrogen-steam, oxygen-nitrogen and oxygen-nitrogen-steam is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is not achieved and the dispersibility can be hardly recovered so that recovery of the catalytic activity is not observed (Catalysts C₂₈ -1 to C₂₈ -5). In the case of treatment with an inorganic alkaline substance at room temperature, elimination of sulfurous materials is accomplished, but no catalytic activity is recognized (Catalyst D₂₈ -5). When treated with an inorganic alkaline substance under heating, elimination of sulfurous materials and recovery of the dispersibility as well as recovery of the catalytic activity are good (Catalysts D₂₈ -1 to D₂₈ -4).

                                      TABLE 28                                     __________________________________________________________________________                Reactivated                                                         Catalyst   A.sub.28                                                                          B.sub.28                                                                          C.sub.28 -1                                                                        C.sub.28 -2                                                                         C.sub.28 -3                                                                         C.sub.28 -4                                                                         C.sub.28 -5                                                                         D.sub.28 -1                                                                        D.sub.28 -2                                                                         D.sub.28 -3                                                                         D.sub.28 -4                                                                        D.sub.28            __________________________________________________________________________                                                                -5                  Condi-                                                                              Reacti-     H.sub.2                                                                            H.sub.2 :H.sub.2 O                                                                  H.sub.2 O:N.sub.2                                                                   O.sub.2 :N.sub.2                                                                    O.sub.2 :H.sub.2 O:                                                                 0.375N                                                                             0.375N                                                                              0.375N                                                                              0.375N                                                                             0.375N              tions                                                                               vating                                                                               -- --     (1:1 (3:1 (21:79                                                                              N.sub.2 (10:50                                                                      NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        NaOH                                                                               NaOH                of   agent*)         by mol)                                                                             by mol)                                                                             by   :40 by                                     treat-                         volume)                                                                             volume)                                    ment                                                                           for  Temper-                                                                   reacti-                                                                             ature (°C.)                                                                   -- -- 600 600  650  500  600  100 100  100  50  30                  vation                                                                              Pressure                                                                             -- -- 6.0 6.0  6.0  6.0  6.0  1.0 1.0  1.0  1.0 1.0                      (ata)                                                                          Time (hrs)                                                                           -- -- 6.0 6.0  12.0 5.0  10.0 1.5 3.0  3.0  6.0 10.0                Post-treat-                                                                               -- --  --  --   --   --   --  Water washing: 100° C., 2                                               hrs.                                  ment                                     Drying: 100° C., 16 hrs.       Elimina-                                                                            Carbo-                                                                               -- -- 76  78   100  100  100  44  43   40   35  30                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                            -- -- 28  31   34   42   40   88  86   82   79  73                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                           43 25 25  25   25   23   24   34  36   32   31  28                  Conversion of                                                                             89  5 5   5    6    5    6    68  68   65   50  8                   hydrogen (%)                                                                   __________________________________________________________________________

EXAMPLE 33

The reactivated catalysts as obtained in Example 32 (Catalysts C₂₈ -1, C₂₈ -2 and C₂₈ -5) were each subjected to further treatment for reactivation under the conditions as shown in Table 29. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Table 27. The results are shown in Table 29 (Catalysts E₂₉ -1 to E₂₉ -8).

Likewise, the reactivated catalysts as obtained in Example 32 (Catalysts D₂₈ -1 and D₂₈ -4) were each subjected to further treatment for reactivation under the conditions as shown in Table 29. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Table 27. The results are shown in Table 29 (Catalysts E₂₉ -9 to E₂₉ -12).

As seen from Table 29, the catalysts (E₂₉ -1 to E₂₉ -6 and E₂₉ -9 to E₂₉ -12) reactivated in two steps are much more recovered in catalytic activity than the catalysts reactivated in one step.

                                      TABLE 29                                     __________________________________________________________________________     Catalyst    E.sub.29 -1                                                                        E.sub.29 -2                                                                        E.sub.29 -3                                                                         E.sub.29 -4                                                                         E.sub.29 -5                                                                        E.sub.29 -6                                                                        E.sub.29 -7                                                                        E.sub.29 -8                                                                        E.sub.29 -9                                                                       E.sub.29 -10                                                                        E.sub.29 -11                                                                       E.sub.29 -12         Catalyst used                                                                              C.sub.28 -1                                                                        C.sub.28 -1                                                                        C.sub.28 -1                                                                         C.sub.28 -1                                                                         C.sub.28 -2                                                                        C.sub.28 -5                                                                        C.sub.28 -1                                                                        C.sub.28 -1                                                                        D.sub.28 -1                                                                       D.sub.28 -2                                                                         D.sub.28 -3                                                                        D.sub.28             __________________________________________________________________________                                                               -4                   Condi-                                                                              Reactivating                                                                          0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                                                                              0.1N                                                                               0.375N                                                                             0.375N                                                                             0.375N                                                                             H.sub.2                                                                           H.sub.2 O:N.sub.2                                                                   H.sub.2                                                                            H.sub.2                                                                        O:N.sub.2            tions                                                                               agent  NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH   (3:1     (3:1                 of                                               by mol)  by mol)              treat-                                                                         ment                                                                           for  Temperature                                                                           50  80  100  100  100 80  30  30  600                                                                               650  600 650                  reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              1.0 1.0 1.0  1.0  1.0 1.0 1.0 1.0 6.0                                                                               6.0  6.0 6.0                       (ata)                                                                          Time (hrs)                                                                            6.0 1.5 3.0  3.0  1.5 1.5 10.0                                                                               3.0 6.0                                                                               12.0 6.0 12.0                 Post-treat- Water washing: 100° C., 2 hrs.                                                                             --                                                                                --   --  --                  ment        Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 79  84  83   81   81  100 78  78  86 100  85  100                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             83  96  94   88   90  97  80  51  89 87   83  80                   materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      34  41  40   38   40  41  31  30  34 36   32  31                   (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     60  78  75   74   75  78  9   7   78 78   75  65                   (%)                                                                            __________________________________________________________________________

EXAMPLE 34

The reactivated catalysts as obtained in Example 33 (Catalysts E₂₉ -1, E₂₉ -7 and E₂₉ -8) were each subjected to further treatment for reactivation under the conditions as shown in Table 30. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Table 27. The results are shown in Table 30.

As seen from Table 30, the catalysts (F₃₀ -1 to F₃₀ -11) reactivated in three steps are more recovered in catalytic activity than the catalysts reactivated in two steps.

                                      TABLE 30                                     __________________________________________________________________________     Catalyst    F.sub.30 -1                                                                        F.sub.30 -2                                                                         F.sub.30 -3                                                                         F.sub.30 -4                                                                          F.sub.30 -5                                                                         F.sub.30 -6                                                                        F.sub.30 -7                                                                         F.sub.30 -8                                                                         F.sub.30 -9                                                                        F.sub.30 -10                                                                       F.sub.30 -11        Catalyst used                                                                              E.sub.29 -1                                                                        E.sub.29 -1                                                                         E.sub.29 -1                                                                         E.sub.29 -1                                                                          E.sub.29 -1                                                                         E.sub.29 -7                                                                        E.sub.29 -7                                                                         E.sub.29 -7                                                                         E.sub.29 -7                                                                        E.sub.29 -7                                                                        E.sub.29            __________________________________________________________________________                                                                -8                  Condi-                                                                              Reactivating                                                                          0.4%                                                                               0.5% 0.3% 0.3%  0.3% 0.4%                                                                               0.4% 0.3% 0.7%                                                                               2.0%                                                                               1.0%                tions                                                                               agent  Hydra-                                                                             Formal-                                                                             Sodium                                                                              Lithium                                                                              Glucose                                                                             Hydra-                                                                             Formal-                                                                             Sodium                                                                              Sodium                                                                             Sodium                                                                             Hydra-              of          zine                                                                               dehyde                                                                              boro-                                                                               aluminum   zine                                                                               dehyde                                                                              boro-                                                                               tartrate                                                                           formate                                                                            zine                treat-               hydride                                                                             hydride             hydride                          ment                                                                           for  Temperature                                                                           20  20   20   20    20   20  20   20   20  20  60                  reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              1.0 1.0  1.0  1.0   1.0  1.0 1.0  1.0  1.0 1.0 1.0                      (ata)                                                                          Time (hrs)                                                                            3.0 3.0  3.0  3.0   3.0  3.0 3.0  3.0  3.0 3.0 3.0                 Post-treat- Water washing: 75°  C., 3 hrs.                              ment        Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 80  81   81   81    81   80  80   80   80  80  80                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             96  90   95   92    92   92  97   90   91  93  94                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      41  40   40   40    40   37  36   35   36  36  39                  (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     75  74   74   75    73   45  44   42   44  44  49                  (%)                                                                            __________________________________________________________________________

EXAMPLE 35

A catalyst comprising 0.3% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter (hereinafter referred to as "Catalyst A₃₂ ") (1000 ml) was charged into a tubular reactor of 1 inch in diameter, and naphtha (content of sulfur, 2 ppm; final boiling point, 110° C.) and hydrogen were fed therein to effect continuously hydro-cracking reaction for 200 hours under the conditions as shown in Table 31.

                  TABLE 22                                                         ______________________________________                                         Temperature of      265° C.                                             reactor at inlet                                                               Pressure            46 atm. (absolute)                                         Ratio of hydrogen/  1.20 (by mol)                                              hydrocarbon                                                                    Mass velocity       500 kg-mol/m.sup.2 . hr                                    ______________________________________                                    

After 200 hours, the catalyst (hereinafter referred to as "Catalyst B₃₂ ") was treated under the same conditions as shown in Table 32 for reactivation. The reactivated catalyst was reused in hydro-cracking reaction under the same conditions as mentioned above. The results are shown in Table 32.

As seen from Table 32, treatment with a gaseous material is extremely effective in removal of carbonaceous materials but is insufficient in removal of sulfurous materials. In addition, it is almost ineffective in recovery of the dispersibility. Thus, recovery of the catalytic activity is not substantially recognized. Treatment with an inorganic alkaline substance is effective not only in removal of sulfurous materials and recovery of the dispersibility but also in recovery of the catalytic activity.

                                      TABLE 32                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.32                                                                          B.sub.32                                                                          C.sub.32 -1                                                                       C.sub.32 -2                                                                        C.sub.32 -3                                                                        C.sub.32 -4                                                                         C.sub.32 -5                                  __________________________________________________________________________     Condi-                                                                              Reactivity                                                                            -- -- H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                 H.sub.2 O:N.sub.2                                                                  O.sub.2 :N.sub.2                                                                    O.sub.2 :H.sub.2 O:N.sub.2                   tions                                                                               agent           (1:1 by                                                                            (3:1 by                                                                            (21:79 by                                                                           (10:50:40                                    of                   mol)                                                                               mol)                                                                               volume)                                                                             by volume)                                   treat-                                                                         ment                                                                           for  Temperature                                                                           -- -- 600                                                                               600 650 500  600                                          reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              -- -- 6.0                                                                               6.0 6.0 6.0  6.0                                               (ata)                                                                          Time (hrs)                                                                            -- -- 6.0                                                                               6.0 12.0                                                                               5.0  10.0                                              Post-treat-                                                                           -- -- -- --  --  --   --                                                ment                                                                      Elimina-                                                                            Carbo- -- -- 76 78  100 100  100                                          tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- -- 28 31  34  42   40                                           materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      43 25 25 25  25  23   24                                           (m .sup.2 /g-Ru)                                                               Conversion of hydrogen                                                                     89 5  5  6   7   5    5                                            (%)                                                                            __________________________________________________________________________                 Reactivated                                                        Catalyst    D.sub.32 -1                                                                        .sub.32 -2                                                                         D.sub.32 -3                                                                        D.sub.32 -4                                                                        D.sub.32 -5                                                                         D.sub.32 -6                                                                         D.sub.32 -7                                                                        D.sub.32 -8                                                                         D.sub.32 -9                     __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                                                                              0.1N                                                                               0.375N                                                                              0.375N                          tions                                                                               agent*)                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                    of                                                                             treat-                                                                         ment                                                                           for  Temperature                                                                           30  30  50  100 100  100  100 80   100                             reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              1.0 1.0 1.0 1.0 1.0  1.0  1.0 1.0  1.0                                  (ata)                                                                          Time (hrs)                                                                            3.0 10.0                                                                               6.0 3.0 3.0  3.0  3.0 3.0  1.5                                  Post-treat-                                                                           Water washing: 100° C., 2 hrs.                                   ment   Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 10  30  35  47  43   40   29  37   38                              tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             40  73  79  90  86   82   76  78   77                              materials                                                                      (%)                                                                            Specific surface area                                                                      27  28  31  36  36   32   30  31   30                              (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     6   8   50  68  68   68   66  65   60                              (%)                                                                            __________________________________________________________________________

EXAMPLE 36

The reactivated catalysts as obtained in Example 35 (Catalysts D₃₂ -7, D₃₂ -8 and D₃₂ -9) were each subjected to further treatment for reactivation under the conditions as shown in Table 33. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Table 31. The results are shown in Table 33.

As seen from Table 33, the catalysts reactivated in two steps are much more recovered in catalytic activity than the catalysts reactivated in one step.

                                      TABLE 33                                     __________________________________________________________________________     Catalyst    E.sub.33 -1                                                                        E.sub.33 -2                                                                        E.sub.33 -3                                                                          E.sub.33 -4                                                                        E.sub.33 -5                                      Catalyst used                                                                              D.sub.32 -7                                                                        D.sub.32 -7                                                                        D.sub.32 -7                                                                          D.sub.32 -8                                                                        D.sub.32 -9                                      __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          H.sub.2                                                                            H.sub.2 :H.sub.2 0                                                                 O.sub.2 :H.sub.2 O:N.sub.2                                                           H.sub.2                                                                            H.sub.2 :H.sub.2 O                               tions                                                                               agent      (1:1 by                                                                            (10:50:40 (1:1 by                                          of              mol)                                                                               by volume)                                                                               mol)                                             treat-                                                                         ment                                                                           for  Temperature                                                                           600 600 600   650 650                                              reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              6.0 6.0 6.0   6.0 6.0                                                   (ata)                                                                          Time (hrs)                                                                            6.0 6.0 10.0  12.0                                                                               12.0                                                  Post-treat-                                                                           --  --  --    --  --                                                    ment                                                                      Elimina-                                                                            Carbo- 83  85  100   100 100                                              tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             80  81  84    81  82                                               materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      31  31  30    30  30                                               (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     73  73  73    72  68                                               (%)                                                                            __________________________________________________________________________

EXAMPLE 37

The reactivated catalysts as obtained in Example 35 (Catalysts D₃₂ -1 to D₃₂ -5 and D₃₂ -9) were each subjected to further treatment for reactivation under the conditions as shown in Table 34. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Table 31. The results are shown in Table 34.

As seen from Table 34, the catalysts reactivated in two steps are much more recovered in catalytic activity than the catalysts reactivated in one step.

                                      TABLE 34                                     __________________________________________________________________________     Catalyst        F.sub.34 -1                                                                        F.sub.34 -2                                                                        F.sub.34 -3                                                                          F.sub.34 -4                                                                         F.sub.34 -5                                                                         F.sub.34 -6                                                                         F.sub.34 -7                                                                         F.sub.34 -8                                                                        F.sub.34 -9                                                                        F.sub.34 -10         Catalyst used   D.sub.32 -1                                                                        D.sub.32 -2                                                                        D.sub.32 -3                                                                          D.sub.32 -3                                                                         D.sub.32 -3                                                                         D.sub.32 -4                                                                         D.sub.32 -8                                                                         D.sub.32 -8                                                                        D.sub.32 -9                                                                        D.sub.32             __________________________________________________________________________                                                               -9                   Condi- Reactivating                                                                            1.0%                                                                               0.4%                                                                               0.3%  0.5% 0.3% 0.3% 0.5% 0.7%                                                                               0.4%                                                                               2.0%                 tions  agent    Hydra-                                                                             Hydra-                                                                             Lithium                                                                              Formal-                                                                             Sodium                                                                              Glucose                                                                             Formal-                                                                             Sodium                                                                             Hydra-                                                                             Sodium               of              zine                                                                               zine                                                                               aluminum                                                                             dehyde                                                                              boro-     dehyde                                                                              tartrate                                                                           zine                                                                               formate              treat-                  hydride    hydride                                     ment   Temperature                                                                             60  20  20    20   20   20   20   20  20  20                   for    (°C.)                                                            reacti-                                                                               Pressure 1.0 1.0 1.0   1.0  1.0  1.0  1.0  1.0 1.0 1.0                  vation (ata)                                                                          Time (hrs)                                                                              3.0 3.0 3.0   3.0  3.0  3.0  3.0  3.0 3.0 3.0                         Post-treat-                                                                             Water washing: 75° C., 3 hrs.                                  ment     Drying: 100° C., 16 hrs.                                Elimina-                                                                              Carbo-   10  30  35    35   35   47   37   37  38  38                   tion per-                                                                             naceous                                                                 centage                                                                               materials                                                               of                                                                             poisonous                                                                             Sulfurous                                                                               90  91  95    95   95   98   90   89  92  90                   materials                                                                             materials                                                               (%)                                                                            Specific surface area                                                                          37  38  38    38   37   41   38   38  38  38                   (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                         70  70  71    68   70   71   70   70  71  72                   (%)                                                                            __________________________________________________________________________

EXAMPLE 38

The reactivated catalysts as obtained in Example 37 (Catalysts F₃₄ -1, F₃₄ -3 and F₃₄ -5 to F₃₄ -7) were each subjected to further treatment for reactivation under the conditions as shown in Table 35. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Table 31. The results are shown in Table 35.

As seen from Table 35, the catalysts (G₃₅ -1 to G₃₅ -5) reactivated in three steps are much more recovered in catalytic activity than the catalysts reactivated in two step.

                                      TABLE 35                                     __________________________________________________________________________     Catalyst    G.sub.35 -1                                                                        G.sub.35 -2                                                                        G.sub.35 -3                                                                         G.sub.35 -4                                                                         G.sub.35 -5                                      Catalyst used                                                                              F.sub.34 -1                                                                        F.sub.34 -3                                                                        F.sub.34 -5                                                                         F.sub.34 -6                                                                         F.sub.34 -7                                      __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          H.sub.2                                                                            H.sub.2                                                                            H.sub.2 :H.sub.2 O                                                                  H.sub.2 O:N.sub.2                                                                   O.sub.2 :H.sub.2 0:N.sub.2                       tions                                                                               agent          (1:1 by                                                                             (3:1 by                                                                             (10:50:40                                        of                  mol) mol) by volume)                                       treat-                                                                         ment                                                                           for  Temperature                                                                           650 600 600  650  600                                              reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              6.0 6.0 6.0  6.0  6.0                                                   (ata)                                                                          Time (hrs)                                                                            12.0                                                                               6.0 6.0  12.0 10.0                                                  Post-treat-                                                                           --  --  --   --   --                                                    ment                                                                      Elimina-                                                                            Carbo- 100 84  85   100  100                                              tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             96  97  97   97   96                                               materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      38  39  38   41   39                                               (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     77  78  76   79   78                                               (%)                                                                            __________________________________________________________________________

EXAMPLE 39

The reactivated catalysts (Catalysts E₃₃ -1 and G₃₅ -4) respectively as obtained in Examples 36 and 38 were reused for continuous hydro-cracking under the conditions as shown in Table 31. The reactivated catalysts showed the same tendency as a freshly prepared catalyst (Catalyst A₃₂) in depression of the catalytic activity.

EXAMPLE 40

A catalyst comprising 0.3% of platinum deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₃₇ ") (1000 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising naphtha (content of sulfur, 2 ppm; final boiling point, 105° C.) and hydrogen was fed therein to effect continuous hydro-cracking reaction for 200 hours under the conditions as shown in Table 36.

                  TABLE 36                                                         ______________________________________                                         Temperature of      260° C.                                             reactor at inlet                                                               Pressure            46 atm. (absolute)                                         Ratio of hydrogen/  1.4 (by mol)                                               hydrocarbon                                                                    Mass velocity       500 kg-mol/m.sup.2.hr                                      ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₃₇ ") was treated under the conditions as shown in Table 37 for reactivation. The reactivated catalyst was reused in hydro-cracking reaction under the same conditions as mentioned above. The results are shown in Table 37.

As seen from Table 37, the reactivation treatment with hydrogen or hydrogen-steam is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalysts C₃₇ -1 and C₃₇ -2). In the case of treatment with an inorganic alkaline substance at room temperature for a long time, elimination of sulfurous materials and recovery of the dispersibility are good, but recovery of the catalytic activity is not well recognized (Catalysts D₃₇ -1 and D₃₇ -2). When treated with an inorganic alkaline substance under heating, the catalytic activity is highly recovered.

                                      TABLE 37                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.37                                                                          B.sub.37                                                                          C.sub.37 -1                                                                       C.sub.37 -2                                                                         D.sub.37 -1                                                                        D.sub.37 -2                                                                        D.sub.37 -3                                                                        D.sub.37 -4                                                                         D.sub.37 -5                         __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          -- -- H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                  0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                              tions                                                                               agent*)         (1:1 by                                                                             NaOH                                                                               NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                        of                   mol)                                                      treat-                                                                         ment                                                                           for  Temperature                                                                           -- -- 600                                                                               600  30  50  100 100  100                                 reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              -- -- 6.0                                                                               6.0  1.0 1.0 1.0 1.0  1.0                                      (ata)                                                                          Time (hrs)                                                                            -- -- 6.0                                                                               6.0  10.0                                                                               6.0 1.5 3.0  3.0                                      Post-treat-                                                                           -- -- -- --   Water washing: 100° C., 2 hrs.                     ment                 Drying: 100° C., 16 hrs.                      Elimina-                                                                            Carbo- -- -- 76 78   30  35  44  43   40                                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             -- -- 26 31   73  79  88  86   82                                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      42 24 24 25   27  30  34  37   32                                  (m.sup.2 /g-Ru)                                                                Conversion of hydrogen                                                                     85 5  7  6    5   50  68  69   69                                  (%)                                                                            __________________________________________________________________________

EXAMPLE 41

A catalyst comprising 1.0% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₃₉ ") (250 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising methanol (content of sulfur, 1 ppm) and hydrogen was fed therein to effect continuously hydro-cracking reaction for 200 hours under the conditions as shown in Table 38.

                  TABLE 38                                                         ______________________________________                                         Temperature of      470° C.                                             reactor at inlet                                                               Pressure            10 atm. (absolute)                                         Ratio of hydrogen/  1.1 (by mol)                                               methanol                                                                       Mass velocity       500 kg-mol/m.sup.2.hr                                      ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₃₉ ") was treated under the conditions as shown in Table 39 for reactivation. The reactivated catalyst was reused in hydro-cracking reaction under the same conditions as mentioned above. The results are shown in Table 39.

As seen from Table 39, the reactivation treatment with hydrogen or hydrogen-steam is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalysts C₃₉ -1 and C₃₉ -2). In the case of treatment with an inorganic alkaline substance at room temperature for a long time, elimination of sulfurous materials and recovery of the dispersibility are good, but recovery of the catalytic activity is not well recognized (Catalysts D₃₉ -1 and D₃₉ -2). When treated with an inorganic alkaline substance under heating, the catalytic activity is highly recovered (Catalysts D₃₉ -3 to D₃₉ -5). Sole treatment with an aqueous solution of a reducing substance is effective in elimination of sulfurous materials but not in elimination of carbonaceous materials. Nevertheless, a tendency to recovery of the catalytic activity is seen (Catalysts D₃₉ -6 to D₃₉ -8).

                                      TABLE 39                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.39                                                                          B.sub.39                                                                          C.sub.39 -1                                                                       C.sub.39 -2                                                                         D.sub.39 -1                                                                        D.sub.39 -2                                                                        D.sub.39 -3                                                                        D.sub.39 -4                                                                         D.sub.39 -5                                                                         D.sub.39 -6                                                                         D.sub.39                                                                            D.sub.39             __________________________________________________________________________                                                               -8                   Condi-                                                                              Reactivating H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                  0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                                                                              0.4 %                                                                               0.3                                                                                 1.0 %                tions                                                                               agent  -- --    (1:1 by                                                                             NaOH                                                                               NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        Hydra-                                                                              Glu- Form-                of                   mol)                       zine cose alde-                treat-                                                    hyde                 ment                                                                           for  Temperature                                                                           -- -- 600                                                                               600  30  50  100 100  100  20   20   60                   reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                       (ata)  -- -- 6.0                                                                               6.0  1.0 1.0 1.0 1.0  1.0  1.0  1.0  1.0                       Time (hrs)                                                                            -- -- 6.0                                                                               6.0  10.0                                                                               6.0 1.5 3.0  3.0  3.0  3.0  3.0                        Post-treat-         Water washing: 100° C., 2                                                                     Water washing: 75°                                                      C., 3 hrs.                          ment   -- -- -- --   Drying: 100° C., 16 hrs.                                                                      Drying: 100° C.,                                                        16 hrs.                        Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               -- -- 75 76   10  35  45  43   40   0    0    0                    centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             -- -- 24 25   40  80  89  85   84   70   51   69                   (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                            42 18 18 18   22  26  31  30   28   26   27   27                   Amount of catalyst                                                             required (ml)                                                                              80 -- -- --   200 148 120 122  130  152  151  150                  __________________________________________________________________________

EXAMPLE 42

The reactivated catalysts as obtained in Example 41 (Catalysts D₃₉ -1 to D₃₉ -4) were each subjected to further treatment for reactivation under the conditions as shown in Table 40. The thus reactivated catalysts were each reused for continuous hydro-cracking under the same conditions as shown in Table 38. The results are shown in Table 40.

As seen from Table 40, the catalysts (E₄₀ -1 to E₄₀ -5) are effectively recovered in catalytic activity.

                                      TABLE 40                                     __________________________________________________________________________     Catalyst    E.sub.40 -1                                                                        E.sub.40 -2                                                                        E.sub.40 -3                                                                        E.sub.40 -4                                                                         E.sub.40 -5                                       Catalyst used                                                                              D.sub.39 -1                                                                        D.sub.39 -2                                                                        D.sub.39 -3                                                                        D.sub.39 -3                                                                         D.sub.39 -4                                       __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          1.0%                                                                               0.4%                                                                               0.4%                                                                               0.5% 0.4%                                              tions                                                                               agent  Hydra-                                                                             Hydra-                                                                             Hydra-                                                                             Formal-                                                                             Hydra-                                            of          zine                                                                               zine                                                                               zine                                                                               dehyde                                                                              zine                                              treat-                                                                         ment                                                                           for  Temperature                                                                           60  20  20  20   20                                                reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              1.0 1.0 1.0 1.0  1.0                                                    (ata)                                                                          Time (hrs)                                                                            3.0 3.0 3.0 3.0  3.0                                                    Post-treat-                                                                           Water washing: 75° C., 3 hrs.                                    ment   Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 10  35  45  45   43                                                tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             90  94  96  98   96                                                materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      30  32  35  35   34                                                (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         122 110 95  95   98                                                required (ml)                                                                  __________________________________________________________________________

EXAMPLE 43

A catalyst comprising 1.5% of ruthenium and 0.1% of chromium oxide deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₄₁ ") (290 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising methane and air was fed therein to effect continuously partial combustion reaction for 500 hours under the following conditions:

Temperature of reactor: inlet, 310° C., outlet, 700° C.;

Space velocity: 17500 (1/hr);

Ratio of air/methane: 2.37 (by mol);

Pressure: 1 atm. (absolute)

After 500 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₄₁ ") was treated under the conditions as shown in Table 41 for reactivation. The reactivated catalyst was reused in partial combustion reaction under the same conditions as mentioned above. The results are shown in Table 41.

As seen from Table 41, the reactivation treatment with hydrogen is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalyst C₄₁ -1). In the case of treatment with an inorganic alkaline substance at room temperature for a long time, elimination of sulfurous materials and recovery of the dispersibility are good, but recovery of the catalytic activity is not well recognized (Catalysts D₄₁ -1 and D₄₁ -2). Treatment with an inorganic alkaline substance under heating is per se effective in recovery of the catalytic activity (Catalysts D₄₁ -3 to D₄₁ -5 and D₄₁ -14 to D₄₁ -16). Treatment with an aqueous solution of a reducing substance is effective in elimination of sulfurous materials but not in elimination of carbonaceous materials and recovery of the dispersibility. Nevertheless, a tendency to recovery of the catalytic activity is seen (Catalysts D₄₁ -6 to D₄₁ -13).

                                      TABLE 41                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.41                                                                          B.sub.41                                                                          C.sub.41 -1                                                                       D.sub.41 -1                                                                        D.sub.41 -2                                                                        D.sub.41 -3                                                                        D.sub.41 -4                                                                        D.sub.41 -5                                                                        D.sub.41 -6                                                                        D.sub.41 -7                       __________________________________________________________________________     Condi-                                                                             Reactivating  H.sub.2                                                                           0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                             0.4%                                                                               0.3%                              tions                                                                              agent   -- --    NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                                                                               Hydra-                                                                             Lithium                           of                                       zine                                                                               aluminum                          treat-                                       hydride                           for Temperature                                                                            -- -- 650                                                                               30  30  50  100 148 20  20                                reacti-                                                                            (°C.)                                                               vation                                                                             Pressure                                                                               -- -- 6.0                                                                               1.0 1.0 1.0 1.0 5.0 1.0 1.0                                   (ata)                                                                          Time (hrs)                                                                             -- -- 12.0                                                                              3.0 10.0                                                                               6.0 3.0 1.0 3.0 3.0                                   Post-treat-                      Water washing: 75° C.,                 ment    -- -- -- Water washing: 100° C., 2 hrs.                                                             3 hrs.                                                      Drying: 100° C., 16 hrs.                                                                Drying: 100°C., 16 hrs.            Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               -- -- 100                                                                               12  41  43  52  58  0   0                                 centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             -- -- 31 32  72  78  95  100 70  51                                (%)                                                                            Specific surface area                                                                      43 17 17 21  26  28  33  34  19  21                                (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         51 -- -- --  --  150 105 100 174 170                               required (ml)                                                                  __________________________________________________________________________                 Reactivated                                                        Catalyst    D.sub.41 -8                                                                        D.sub.41 -9                                                                        D.sub.41 -10                                                                       D.sub.41 -11                                                                       D.sub.41 -12                                                                       D.sub.41 -13                                                                       D.sub.41 -14                                                                       D.sub.41 -15                                                                        D.sub.41 -16                      __________________________________________________________________________     Condi-                                                                             Reactivating                                                                           0.7%                                                                               2.0%                                                                               0.3%                                                                               1.0%                                                                               1.0%                                                                               1.0%                                                                               3.0N                                                                               0.375N                                                                              0.375N                            tions                                                                              agent   Sodium                                                                             Sodium                                                                             Glu-                                                                               Hydra-                                                                             Form-                                                                              Sodium                                                                             NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                      of          tart-                                                                              for-                                                                               cose                                                                               zine                                                                               alde-                                                                              borohy-                                        treat-      rate                                                                               mate        hyde                                                                               dride                                          ment                                                                           for Temperature                                                                            20  20  20  60  60  60  100 100  100                               reacti-                                                                            (°C.)                                                               vation                                                                             Pressure                                                                               1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0  1.0                                   (ata)                                                                          Time (hrs)                                                                             3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0  3.0                                   Post-treat-                     Water washing: 100° C.,                 ment    Water washing: 75° C., 3 hrs.                                                                   2 hrs.                                                 Drying: 100° C., 16 hrs.                                                                        Drying: 100° C., 16 hrs.            Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               0   0   0   0   0   0   54  50   48                                centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             50  55  51  92  70  90  97  94   91                                (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                            21  21  21  21  21  21  34  32   30                                Amount of catalyst                                                                         172 172 174 166 170 174 101 107  110                               required (ml)                                                                  __________________________________________________________________________

EXAMPLE 44

The reactivated catalysts as obtained in Example 43 (Catalysts D₄₁ -1 to D₄₁ -13) were each subjected to further treatment for reactivation under the conditions as shown in Table 42. The thus reactivated catalysts were each reused for continuous partial combustion under the same conditions as shown in Example 43. The results are shown in Table 42.

As seen from Table 42, the treatment for reactivation at the second step is quite effective for recovery of the catalytic activity.

                                      TABLE 42                                     __________________________________________________________________________     Catalyst        E.sub.42 -1                                                                          E.sub.42 -2                                                                          E.sub.42 -3                                                                        E.sub.42 -4                                                                        E.sub.42 -5                                                                          E.sub.42 -6                                                                         E.sub.42 -7                                                                        E.sub.42 -8                                                                        E.sub.42 -9                                                                        E.sub.42 -10        Catalyst used   D.sub.41 -1                                                                          D.sub.41 -2                                                                          D.sub.41 -3                                                                        D.sub.41 -3                                                                        D.sub.41 -4                                                                          D.sub.41 -4                                                                         D.sub.41 -6                                                                        D.sub.41 -6                                                                        D.sub.41 -11                                                                       D.sub.41            __________________________________________________________________________                                                                -12                 Condi-                                                                              Reactivating                                                                              1.0%  0.4%  0.4%                                                                               0.5%                                                                               0.4%  0.3% 0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N              tions                                                                               agent      Hydra-                                                                               Hydra-                                                                               Hydra-                                                                             Formal-                                                                            Hydra-                                                                               Sodium                                                                              NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                of              zine  zine  zine                                                                               dehyde                                                                             zine  boro-                                treat-                                    hydride                              ment                                                                           for  Temperature                                                                               60    20    20  20  20    20   50  100 100 80                  reacti-                                                                             (°C.)                                                              vation                                                                              Pressure   1.0   1.0   1.0 1.0 1.0   1.0  1.0 1.0 1.0 1.0                      (ata)                                                                          Time (hrs) 3.0   3.0   3.0 3.0 3.0   3.0  6.0 3.0 3.0 3.0                      Post-treat-                                                                               Water washing: 75° C., 3 hrs.                                                                          Water Washing: 100°                                                     C., 2 hrs.                           ment       Drying: 100° C., 16 hrs.                                                                               Drying: 100° C., 16                                                     hrs.                            Elimina-                                                                            Carbo-     12    41    43  43  52    52   43  54  53  47                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous  91    93    95  95  97    96   92  97  96  92                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                          34    36    36  36  40    40   35  39  41  39                  (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                             150   160   101 105 75    77   103 76  74  90                  required (ml)                                                                  __________________________________________________________________________     Catalyst        E.sub.42 -11                                                                         E.sub.42 -12                                                                         E.sub.42 -13                                                                       E.sub.42 -14                                                                       E.sub.42 -15                                                                         E.sub.42 -16                                                                        E.sub.42 -17                                                                       E.sub.42 -18                                                                       E.sub.42 -19                                                                       E.sub.42 -20        Catalyst used   D.sub.41 -1                                                                          D.sub.41 -2                                                                          D.sub.41 -3                                                                        D.sub.41 -3                                                                        D.sub.41 -4                                                                          D.sub.41 -4                                                                         D.sub.41 -7                                                                        D.sub.41 -8                                                                        D.sub.41 -9                                                                        D.sub.41            __________________________________________________________________________                                                                -9                  Condi-                                                                              Reactivating                                                                              0.3%  0.3%  0.7%                                                                               2.0%                                                                               0.3%  0.3% 0.375N                                                                             0.1N                                                                               0.375N                                                                             0.375N              tions                                                                               agent      Lithium                                                                              Lithium                                                                              Sodium                                                                             Sodium                                                                             Lithium                                                                              Glucose                                                                             NaOH                                                                               NaOH                                                                               NaOH                                                                               NaOH                of              aluminum                                                                             aluminum                                                                             tart-                                                                              formate                                                                            aluminum                                   treat-          hydride                                                                              hydride                                                                              rate    hydride                                    ment                                                                           for  Temperature                                                                               20    20    20  20  20    20   50  100 100 80                  reacti-                                                                             (°C.)                                                              vation                                                                              Pressure   1.0   1.0   1.0 1.0 1.0   1.0  1.0 1.0 1.0 1.0                      (ata)                                                                          Time (hrs) 3.0   3.0   3.0 3.0 3.0   3.0  6.0 3.0 1.5 3.0                      Post-treat-                                                                               Water washing: 75° C., 3 hrs.                                                                          Water washing: 100°                                                     C., 2 hrs.                           ment       Drying: 100° C., 16 hrs.                                                                               Drying: 100° C., 16                                                     hrs.                            Elimina-                                                                            Carbo-     12    41    43  43  52    52   43  44  46  47                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous  68    88    91  92  96    96   91  90  94  93                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                          31    36    37  37  41    40   38  37  37  37                  (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                             149   154   102 110 76    77   115 72  80  92                  required (ml)                                                                  __________________________________________________________________________

EXAMPLE 45

The reactivated catalyst as obtained in Example 43 (Catalyst D₄₁ -3) was treated with a 0.7% aqueous solution of sodium tartrate at 20° C. under 1 atom. (absolute) for 3 hours, washed with water at 75° C. for 3 hours and dried at 100° C. for 16 hours. Then, the resulting catalyst was again subjected to treatment with a 0.375 N aqueous solution of sodium hydroxide at 50° C. under 1 atom. (absolute) for 6 hours and treatment with a 0.7% aqueous solution of sodium tartrate at 20° C. under 1 atom. (absolute) for 3 hours, followed by washing with water at 75° C. for 3 hours and drying at 100° C. for 16 hours. The thus reactivated catalyst was used for partial combustion under the same conditions as shown in Example 43. The results are shown in Table 43, from which it is understood that the repeating treatments are quite effective in recovery of the catalytic activity. T1 TABLE 43Catalyst? F? Elimination Carbonaceous 75 percentage materials of poison- ous mate- Sulfurous 100 rials (%) materials Specific surface area 42 (m² /g-Ru) Amount of catalyst required 58 (ml)?

EXAMPLE 46

The reactivated catalyst as obtained in Example 44 (Catalyst E₄₂ -5) was used for continuous partial combustion under the conditions as shown in Example 43. The reactivated catalyst showed the same tendency as a freshly prepared catalyst in depression of the catalytic activity.

EXAMPLE 47

A catalyst comprising 1.7% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₄₅ ") (290 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising methane and air was fed therein to effect continuously partial combustion reaction for 300 hours under the conditions as shown in Table 44.

                  TABLE 44                                                         ______________________________________                                         Temperature of  at inlet     310° C.                                    reactor         at oulet     700° C.                                    Space velocity           17500 hr.sup.-1                                       Ratio of air/methane     2.37 (by mol)                                         Pressure                 1 atm.                                                                         (absolute)                                            ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₄₅ ") was treated under the conditions as shown in Table 45 for reactivation. The reactivated catalyst was reused in partial combustion reaction under the same conditions as mentioned above. The results are shown in Table 45.

As seen from Table 45, the reactivation treatment with a gaseous material such as hydrogen, hydrogen-steam, oxygen-nitrogen or oxygen-nitrogen-steam is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed (Catalysts C₄₅ -1 to C₄₅ -5). In the case of treatment with an inorganic alkaline substance at room temperature, elimination of sulfurous materials is good but recovery of the catalytic activity is not seen. Treatment with an inorganic alkaline substance under heating is effective in elimination of sulfurous materials and recovery of the dispersibility, and recovery of the catalytic activity is recognized.

                                      TABLE 45                                     __________________________________________________________________________                     Reactivated                                                    Catalyst  A.sub.45                                                                          B.sub.45                                                                          C.sub.45 -1                                                                        C.sub.45 -2                                                                         C.sub.45 -3                                                                         C.sub.45 -4                                                                         C.sub.45 -5                                                                          D.sub.45 -1                                                                        D.sub.45 -2                                                                         D.sub.45 -3                                                                         D.sub.45 -4                                                                        D.sub.45            __________________________________________________________________________                                                                -5                  Condi-                                                                             Reacti-                                                                              -- -- H.sub.2                                                                            H.sub.2 :H.sub.2 O                                                                  H.sub.2 O:N.sub.2                                                                   O.sub.2 :N.sub.2                                                                    O.sub.2 :H.sub.2 O:N.sub.2                                                           0.375N                                                                             0.375N                                                                              0.375N                                                                              0.375N                                                                             0.375N              tions                                                                              vating          (1:1 by                                                                             (3:1 by                                                                             (21:79 by                                                                           (10:50:40                                                                            NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        NaOH                                                                               NaOH                of  agent           mol) mol) volume)                                                                             by volume)                                  treat-                                                                         ment                                                                           for Temper-                                                                              -- -- 600 600  650  500  600   100 100  100  50  30                  reacti-                                                                            ature (°C.)                                                         vation                                                                             Pressure                                                                             -- -- 6.0 6.0  6.0  6.0  6.0   1.0 1.0  1.0  1.0 1.0                     (ata)                                                                          Time (hrs)                                                                           -- -- 6.0 6.0  12.0 5.0  10.0  1.5 3.0  3.0  6.0 10.0                    Post-treat-                                                                          -- -- --  --   --   --   --    Water washing: 100° C., 2                                               hrs.                                      ment                                 Drying: 100° C., 16 hrs.       Elimina-                                                                            Carbo-                                                                              -- -- 78  80   100  100  100   55  54   50   41  40                  tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                           -- -- 23  30   34   42   40    97  95   89   80  77                  materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                    43 19 19  19   19   17   18    35  36   33   28  28                  (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                       65 -- --  --   --   --   --    108 101  110  150 --                  required (ml)                                                                  __________________________________________________________________________

EXAMPLE 48

The reactivated catalysts as obtained in Example 47 (Catalysts C₄₅ -1, C₄₅ -2 and C₄₅ -5) were each subjected to further treatment for reactivation under the conditions as shown in Table 46. The thus reactivated catalysts (Catalysts E₄₆ -1 to E₄₆ -7) were each reused for continuous partial combustion under the same conditions as shown in Table 44. The results are shown in Table 46, from which it is understood that the treatment with an inorganic alkaline substance under heating at the second step is quite effective in recovery of the catalytic activity.

                                      TABLE 46                                     __________________________________________________________________________      Catalyst    E.sub.46 -1                                                                       E.sub.46 -2                                                                        E.sub.46 -3                                                                        E.sub.46 -4                                                                         E.sub.46 -5                                                                        E.sub.46 -6                                                                        E.sub.46 -7                               Catalyst used                                                                              C.sub.45 -1                                                                        C.sub.45 -1                                                                        C.sub.45 -1                                                                        C.sub.45 -1                                                                         C.sub.45 -2                                                                        C.sub.45 -5                                                                        C.sub.45 -1                               __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                              0.1N                                                                               0.375N                                                                             0.375N                                    tions                                                                               agent  NaOH                                                                               NaOH                                                                               NaOH                                                                               Ba(OH).sub.2                                                                        NaOH                                                                               NaOH                                                                               NaOH                                      of                                                                             treat-                                                                         ment                                                                           for  Temperature                                                                           50  80  100 100  100 80  30                                        reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              1.0 1.0 1.0 1.0  1.0 1.0 1.0                                            (ata)                                                                          Time (hrs)                                                                            3.0 1.5 1.5 2.0  1.5 1.5 10.0                                      Post-treat  Water washing: 100° C., 2 hrs.                              ment        Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 81  86  85  83   83  100 80                                        tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             85  98  96  90   92  99  82                                        materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      31  38  37  37   37  38  28                                        (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         142 115 101 106  117 120 --                                        required (ml)                                                                  __________________________________________________________________________

EXAMPLE 49

The reactivated catalysts as obtained in Example 48 (Catalyst E₄₆ -1) were each subjected to further treatment for reactivation under the conditions as shown in Table 47. The thus reactivated catalysts (Catalysts F₄₇ -1 to F₄₇ -5) were each reused for continuous partial combustion under the same conditions as shown in Table 44. The results are shown in Table 47, from which it is understood that the treatment for reactivation in three steps results in higher recovery of the catalytic activity.

                                      TABLE 47                                     __________________________________________________________________________      Catalyst    F.sub.47 -1                                                                       F.sub.47 -2                                                                        F.sub.47 -3                                                                         F.sub.47 -4                                                                          F.sub.47 -5                                     Catalyst used                                                                              E.sub.46 -1                                                                        E.sub.46 -1                                                                        E.sub.46 -1                                                                         E.sub.46 -1                                                                          E.sub.46 -1                                     __________________________________________________________________________     Condi-                                                                              Reactivating                                                                          0.4%                                                                               0.5%                                                                               0.3% 0.3%  0.3%                                            tions                                                                               agent  Hydra-                                                                             Form-                                                                              Sodium                                                                              Lithum                                                                               Glucose                                         of          zine                                                                               alde-                                                                              boro-                                                                               aluminum                                              treat-          hyde                                                                               hydride                                                                             hydride                                               ment                                                                           for  Temperature                                                                           20  20  20   20    20                                              reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              1.0 1.0 1.0  1.0   1.0                                                  (ata)                                                                          Time (hrs)                                                                            3.0 3.0 3.0  3.0   3.0                                             Post-treat- Water washing: 75° C., 3 hrs.                               ment        Drying: 100° C., 16 hrs.                                    Elimina-                                                                            Carbo- 82  82  82   82    82                                              tion per-                                                                           naceous                                                                   centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                             98  92  97   94    94                                              materials                                                                           materials                                                                 (%)                                                                            Specific surface area                                                                      40  39  39   39    39                                              (M.sup.2 /g-Ru)                                                                Amount of catalyst                                                                         70  72  72   70    72                                              required (ml)                                                                  __________________________________________________________________________

EXAMPLE 50

A catalyst comprising 1.0% of ruthenium and 0.1% of chromium oxide deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₄₉ ") (290 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising methane and air was fed therein to effect continuously partial combustion reaction for 300 hours under the conditions as shown in Table 48.

                  TABLE 48                                                         ______________________________________                                         Temperature of                                                                               at inlet    310° C.                                       reactor       at outlet   700°  C.                                      Space velocity        17500 hr.sup.-1                                          Ratio of air/methane  2.37 (by mol)                                            Pressure              1 atm.                                                                         (absolute)                                               ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₄₉ ") was treated under the conditions as shown in Table 49 for reactivation. The reactivated catalyst was reused in partial combustion reaction under the same conditions as mentioned above. The results are shown in Table 49.

As seen from Table 49, the reactivation treatment with a gaseous material is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed. In the case of treatment with an inorganic alkaline substance, elimination of sulfurous materials and recovery of the dispersibility as well as recovery of the catalytic activity are good.

                                      TABLE 49                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.49                                                                          B.sub.49                                                                          C.sub.49 -1                                                                       C.sub.49 -2                                                                         D.sub.49 -1                                                                         D.sub.49 -2                                                                         D.sub.49 -3                                __________________________________________________________________________     Condi-                                                                              Reactivating H.sub.2                                                                           O.sub.2 :H.sub.2 O:                                                                 0.375N                                                                              0.1N 0.375N                                     tions                                                                               agent  -- --    N.sub.2 (10:                                                                        NaOH NaOH Na.sub.2 CO.sub.3                          of                   50:40 by                                                  treat-               volume)                                                   ment                                                                           for  Temperature                                                                           -- -- 600                                                                               600  50   100  100                                        reacti-                                                                             (°C.)                                                              vation                                                                              Pressure                                                                              -- -- 6.0                                                                               6.0  1.0  1.0  1.0                                             (ata)                                                                          Time (hrs)                                                                            -- -- 6.0                                                                               10.0 6.0  3.0  3.0                                        Post-treat-               Water washing: 100° C., 2 hrs.                ment        -- -- -- --   Drying: 100° C., 16 hrs.                      Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               -- -- 75 100  43   40   51                                         centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             -- -- 21 37   78   80   93                                         (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                            43 17 17 17   28   28   33                                         Amount of catalyst                                                             required (ml)                                                                              83 -- -- --   140  120  115                                        __________________________________________________________________________

EXAMPLE 51

The reactivated catalyst as obtained in Example 50 (Catalyst D₄₉ -2) was subjected to further treatment for reactivation under the conditions as shown in Table 50. The thus reactivated catalyst was reused for continuous partial combustion under the same conditions as shown in Table 48. The results are shown in Table 50, from which is is understood that the catalyst reactivated in two steps is more recovered in catalytic activity than the catalyst reactivated in one step.

                  TABLE 50                                                         ______________________________________                                         Catalyst           E.sub.50 -1                                                                              E.sub.50 -2                                       Catalyst used      D.sub.49 -2                                                                              D.sub.49 -2                                       ______________________________________                                         Condi-    Reactivating H.sub.2   0.sub.2 :H.sub.2 O:N.sub.2                    tions     agent                  (10:50:40                                     of                               by volume)                                    treat-                                                                         ment                                                                           for       Temperature  600       600                                           reacti-   (°C.)                                                         vation                                                                                   Pressure     6.0       6.0                                                     (ata)                                                                          Time (hrs)   6.0       10.0                                                    Post-treat-  --        --                                                      ment                                                                 Elimina-  Carbo-       85        100                                           tion per- naceous                                                              centage   materials                                                            of                                                                             poisonous Sulfurous    85        89                                            materials materials                                                            (%)                                                                            Specific surface area                                                                             29        28                                                (m.sup.2 /g-Ru)                                                                Amount of catalyst 115       114                                               required (ml)                                                                  ______________________________________                                    

EXAMPLE 52

The reactivated catalyst as obtained in Example 50 (Catalysts D₄₉ -1 and D₄₉ -3) was subjected to further treatment for reactivation under the conditions as shown in Table 51. The thus reactivated catalyst was reused for continuous partial combustion under the same conditions as shown in Table 48. The results are shown in Table 51, from which it is understood that the catalyst reactivated in two steps is more recovered in catalytic activity than the catalyst reactivated in one step.

                  TABLE 51                                                         ______________________________________                                          Catalyst       F.sub.51 -1                                                                             F.sub.51 -2                                                                              F.sub.51 -3                                 Catalyst used  D.sub.49 -1                                                                              D.sub.49 -1                                                                              D.sub.49 -3                                 ______________________________________                                         Condi- Reactivating                                                                               0.3%      0.3%    0.3%                                      tions  agent       Lithium   Sodium  Glucose                                   of                 aluminum  boro-                                             treat-             hydride   hydride                                           ment                                                                           for    Temperature 20        20      20                                        reacti-                                                                               (°C.)                                                            vation                                                                                Pressure    1.0       1.0     1.0                                              (ata)                                                                          Time (hrs)  3.0       3.0     3.0                                       Post-treat-    Water washing: 75° C., 3 hrs.                            ment           Drying: 100° C., 16 hrs.                                 Elimina-                                                                              Carbo-      43        43      52                                        tion per-                                                                             naceous                                                                 centage                                                                               materials                                                               of                                                                             poisonous                                                                             Sulfurous   96        96      97                                        materials                                                                             materials                                                               (%)                                                                            Specific surface area                                                                         34        32        38                                          (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                            94        97        90                                          required (ml)                                                                  ______________________________________                                    

EXAMPLE 53

The reactivated catalyst as obtained in Example 52 (Catalysts F₅₁ -1 to F₅₁ -3) were each subjected to further treatment for reactivation under the conditions as shown in Table 52. The thus reactivated catalyst were each reused for continuous partial combustion under the same conditions as shown in Table 48. The results are shown in Table 52, from which it is understood that the catalysts reactivated in three steps are more recovered in catalytic activity than the catalyst reactivated in two steps.

                  TABLE 52                                                         ______________________________________                                         Catalyst        G.sub.52 -1                                                                             G.sub.52 -2                                                                              G.sub.52 -3                                 Catalyst used   F.sub.51 -1                                                                             F.sub.51 -2                                                                              F.sub.51 -3                                 ______________________________________                                         Condi-  Reactivating                                                                               H.sub.2  H.sub.2 :H.sub.2 O                                                                     H.sub.2 O:N.sub.2                         tions   agent                (1:1 by (3-1 by                                   of                           mol)    mol)                                      treat-                                                                         ment                                                                           for     Temperature 600      600     650                                       reacti- (°C.)                                                           vation                                                                                 Pressure    6.0      6.0     6.0                                               (ata)                                                                          Time (hrs)  6.0      6.0     12.0                                              Post-treat- --       --      --                                                ment                                                                   Elimina-                                                                               Carbo-      86       87      100                                       tion per-                                                                              naceous                                                                centage materials                                                              of                                                                             poisonous                                                                              Sulfurous   98       98      99                                        materials                                                                              materials                                                              (%)                                                                            Specific surface area                                                                          35       33        38                                          (m.sup.2 /g-Ru)                                                                Amount of catalyst                                                                             92       95        89                                          required (ml)                                                                  ______________________________________                                    

EXAMPLE 54

The reactivated catalysts as obtained in Examples 51 and 53 (Catalysts E₅₀ -1 and G₅₂ -3) were each reused for continuous partial combustion under the same conditions as shown in Table 48. As the result, it was recognized that the reactivated catalysts show the same tendency as a freshly prepared catalyst (Catalyst A₄₉) in depression of the catalytic activity.

EXAMPLE 55

A catalyst comprising 1.0% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₅₄ ") (290 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising methanol (content of sulfur, 5 ppm) and air was fed therein to effect continuously partial combustion for 300 hours under the conditions as shown in Table 53.

                  TABLE 53                                                         ______________________________________                                         Temperature of                                                                               at inlet    280° C.                                       reactor       at outlet   700° C.                                       Space velocity        17500 hr .sup.-1                                         Ratio of air/methanol 2.40 (by mol)                                            Pressure              1 atm.                                                                         (absolute)                                               ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₅₄ ") was treated under the conditions as shown in Table 54 for reactivation. The reactivated catalyst was reused in partial combustion reaction under the same conditions as mentioned above. The results are shown in Table 54.

As seen from Table 54, the reactivation treatment with hydrogen or hydrogen-steam is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed. In the case of treatment with an inorganic alkaline substance at room temperature for a long time, elimination of sulfurous materials and recovery of the dispersibility are good, but recovery of the catalytic activity is insufficient. Treatment with an inorganic alkaline substance under heating is proved to be effective for recovery of the catalytic activity. In treatment with a reducing substance, elimination of sulfurous materials is hardly attained. However, there is a tendency to recovery of the catalytic activity.

                                      TABLE 54                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.54                                                                          B.sub.54                                                                          C.sub.54 -1                                                                       C.sub.54 -2                                                                         D.sub.54 -1                                                                        D.sub.54 -2                                                                        D.sub.54 -3                                                                        D.sub.54 -4                                                                         D.sub.54 -5                                                                         D.sub.54 -6                                                                        D.sub.54 -7                                                                         D.sub.54              __________________________________________________________________________                                                              -8                    Condi-                                                                              Reactivating H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                  0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                                                                              0.4%                                                                               0.3% 1.0%                  tions                                                                               agent  -- --    (1:1 by                                                                             NaOH                                                                               NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        Hydra-                                                                             Glucose                                                                             Formal-               of                   mol)                       zine     dehyde                treat-                                                                         ment                                                                           for  Temperature                                                               reacti-                                                                             (°C.)                                                                          -- -- 600                                                                               600  30  50  100 100  100  20  20   60                    vation                                                                              Pressure                                                                       (ata)  -- -- 6.0                                                                               6.0  1.0 1.0 1.0 1.0  1.0  1.0 1.0  1.0                        Time (hrs)                                                                            -- -- 6.0                                                                               6.0  10.0                                                                               6.0 1.5 3.0  3.0  3.0 3.0  3.0                   Post-treat-               Water washing: 100° C., 2                                                                     Water washing: 75°                                                      C., 3 hrs.                     ment        -- -- -- --   Drying: 100° C., 16 hrs.                                                                      Drying: 100° C.,                                                        16 hrs.                        Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               -- -- 100                                                                               100  41  43  44  43   40   0   0    0                     centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             -- -- 31 32   72  78  95  85   84   72  50   68                    (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                            43 13 13 17   20  24  29  28   26   22  23   23                    Amount of catalyst                                                             required (ml)                                                                              85 -- -- --   --  150 115 120  127  163 161  160                   __________________________________________________________________________

EXAMPLE 56

A catalyst comprising 2.0% of platinum deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₅₆ ") (290 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising methane and air was fed therein to effect continuously partial combustion for 300 hours under the conditions as shown in Table 55.

                  TABLE 55                                                         ______________________________________                                         Temperature of                                                                               at inlet    310° C.                                       reactor       at outlet   700° C.                                       Space velocity        17500 hr .sup.-1                                         Ratio of air/methane  2.37 (by mol)                                            Pressure              1 atm.                                                                         (absolute)                                               ______________________________________                                    

After 300 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₅₆ ") was treated under the conditions as shown in Table 56 for reactivation. The reactivated catalyst was reused in partial combustion reaction under the same conditions as mentioned above. The results are shown in Table 56.

As seen from Table 56, the reactivation treatment with hydrogen or hydrogen-steam is extremely effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed. In the case of treatment with an inorganic alkaline substance at room temperature, elimination of sulfurous materials and recovery of the dispersibility are relatively good when the treating time is long, but recovery of the catalytic activity is insufficient. Treatment with an inorganic alkaline substance under heating is proved to be effective for recovery of the catalytic activity. In treatment with a reducing substance, elimination of sulfurous material is good, but removal of carbonaceous materials is hardly attained. However, there is a tendency to recovery of the catalytic activity.

                                      TABLE 56                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.56                                                                          B.sub.56                                                                          C.sub.56 -1                                                                       C.sub.56 -2                                                                         D.sub.56 -1                                                                        D.sub.56 -2                                                                        D.sub.56 -3                                                                        D.sub.56 -4                                                                         D.sub.56 -5                                                                         D.sub.56 -6                                                                        D.sub.56 -7                                                                         D.sub.56              __________________________________________________________________________                                                              -8                    Condi-                                                                              Reactivating H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                  0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                                                                              0.4%                                                                               0.3% 1.0%                  tions                                                                               agent  -- --    (1:1 by                                                                             NaOH                                                                               NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        Hydra-                                                                             Glu- Form-                 of                mol)                     zine cose                                                                               alde-                      treat-                                                   hyde                  ment                                                                           for  Temperature                                                               reacti-                                                                             (°C.)                                                                          -- -- 600                                                                               600  30  50  100 100  100  20  20   60                    vation                                                                              Pressure                                                                       (ata)  -- -- 6.0                                                                               6.0  1.0 1.0 1.0 1.0  1.0  1.0 1.0  1.0                        Time (hrs)                                                                            -- -- 6.0                                                                               6.0  10.0                                                                               6.0 1.5 3.0  3.0  3.0 3.0  3.0                   Post-treat-               Water washing: 100° C., 2                                                                     Water washing: 75°                                                      C., 3 hrs.                     ment        -- -- -- --   Drying: 100° C., 16 hrs.                                                                      Drying: 100° C.,                                                        16 hrs.                        Elimina-                                                                            Carbo-                                                                    tion per-                                                                           naceous                                                                               -- -- 75 76   40  42  44  43   40   0   0    0                     centage materials                                                              of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             -- -- 22 27   72  79  94  86   86   74  52   70                    (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                            41 15 15 15   22  24  29  28   27   23  24   24                    Amount of catalyst                                                             required (ml)                                                                              48 -- -- --   --  87  73  75   77   90  94   92                    __________________________________________________________________________

EXAMPLE 57

A catalyst comprising 2.0% of ruthenium deposited on spheroidal particles of alumina of 4 mm in diameter as a carrier material (hereinafter referred to as "Catalyst A₅₈ ") (350 ml) was charged into a tubular reactor of 1 inch in diameter, and a gaseous mixture comprising naphtha (content of sulfur, 2 ppm; final boiling point, 108° C.) and air was fed therein to effect continuous partial combustion for 200 hours under the conditions as shown in Table 57.

                  TABLE 57                                                         ______________________________________                                         Temperature of                                                                               at inlet    350° C.                                       reactor       at outlet   900° C.                                       Pressure              1 atm.                                                                         (absolute)                                               Ratio of air/naphtha  14.0 (by mol)                                            Space velocity        17500 cm hr.sup.-1                                       ______________________________________                                    

After 200 hours, the resultant catalyst (hereinafter referred to as "Catalyst B₅₈ ") was treated under the conditions as shown in Table 58 for reactivation. The reactivated catalyst was reused in partial combustion reaction under the same conditions as mentioned above. The results are shown in Table 58.

As seen from Table 58, the reactivation treatment with a gaseous material is effective for elimination of carbonaceous materials, but removal of sulfurous materials is insufficient and the dispersibility can be hardly recovered so that recovery of the catalytic activity is scarcely observed. In the case of treatment with an inorganic alkaline substance at room temperature for a long time, elimination of sulfurous materials and recovery of the dispersibility are good, but recovery of the catalytic activity is not well recognized (Catalyst D₅₈ -1). When treated with an inorganic alkaline substance under heating, the catalytic activity is highly recovered (Catalysts D₅₈ -2to D₅₈ -5). Treatment with an aqueous solution of hydrazine or the like is effective in elimination of sulfurous materials but not in elimination of carbonaceous materials. However, a tendency to recovery of the catalytic activity is recognized (Catalysts D₅₈ -6 to D₅₈ -8).

                                      TABLE 58                                     __________________________________________________________________________                       Reactivated                                                  Catalyst    A.sub.58                                                                          B.sub.58                                                                          C.sub.58 -1                                                                       C.sub.58 -2                                                                         D.sub.58 -2                                                                        D.sub.58 -2                                                                        D.sub.58 -3                                                                        D.sub.58 -5                                                                              D.sub.58 -6                                                                        D.sub.58 -6                                                                         D.sub.58              __________________________________________________________________________                                                              -8                    Condi-                                                                              Reactivating H.sub.2                                                                           H.sub.2 :H.sub.2 O                                                                  0.375N                                                                             0.375N                                                                             0.375N                                                                             0.375N                                                                              0.375N                                                                              0.4%                                                                               0.3% 1.0%                  tions                                                                               agent  -- --    (1:1 by                                                                             NaOH                                                                               NaOH                                                                               NaOH                                                                               Na.sub.2 CO.sub.3                                                                   Ba(OH).sub.2                                                                        Hydra-                                                                             Glu- Form-                 of                   mol)                       zine                                                                               cose alde-                 treat-                                                   hyde                  ment                                                                           for  Temperature                                                               reacti-                                                                             (°C.)                                                                          -- -- 600                                                                               500  30  50  100 100  100  20  20   60                    vation                                                                              Pressure                                                                       (ata)  -- -- 6.0                                                                               6.0  1.0 1.0 1.0 1.0  1.0  1.0 1.0  1.0                        Time (hrs)                                                                            -- -- 6.0                                                                               6.0  10.0                                                                               6.0 1.5 3.0  3.0  3.0 3.0  3.0                   Post-treat-               Water washing: 100° C., 2                                                                     Water washing: 75°                                                      C, 3 hrs.                      ment        -- -- -- --   Drying: 100° C., 16 hrs.                                                                      Drying: 100° C.,                                                        16 hrs.                        Elimina-                                                                            Carbo-                                                                    tion per                                                                            naceous                                                                               -- -- 100                                                                               100  48  51  52  53   51   0   0    0                     centage                                                                             materials                                                                 of                                                                             poisonous                                                                           Sulfurous                                                                 materials                                                                           materials                                                                             -- -- 23 25   70  80  93  90   91   70  51   69                    (%)                                                                            Specific surface area                                                          (m.sup.2 /g-Ru)                                                                            42 11 11 14   17  22  28  29   27   26  27   27                    Amount of catalyst                                                             required (ml)                                                                              80 -- -- --   --  156 118 115  120  155 156  155                   __________________________________________________________________________ 

What is claimed is:
 1. A method for reactivation of a platinum group metal catalyst which comprises contacting a platinum group metal catalyst lowered in the catalytic activity as the result of having been used for partial combustion of hydrocarbons or alkanols with an aqueous solution of an inorganic alkaline compound of alkali metal or alkaline earth metal or mixtures thereof in a concentration of 0.001 to 10 N at a temperature of 5° to 250° C. until the catalytic activity of the catalyst is substantially recovered.
 2. The method according to claim 1, wherein the inorganic alkaline compound is a member selected from the group consisting of hydroxides, carbonates, nitrates and sulfates of sodium, potassium, calcium, magnesium, barium and strontium.
 3. The method according to claim 1, followed by treatment with at least one of hydrogen, oxygen and steam at a temperature of 350° to 750° C. under a pressure of 1 to 50 atm. (absolute) until poisonous materials deposited on the catalyst are eliminated.
 4. The method according to claim 1, wherein the catalyst is previously treated with at least one of hydrogen, oxygen and steam at a temperature of 350° to 750° C. under a pressure of 1 to 10 atm. (absolute) until poisonous materials deposited on the catalyst are eliminated.
 5. The method according to claim 1, wherein the catalyst is previously contacted with an aqueous solution of a reducing substance in a concentration of 0.01 to 10% by weight at a temperature of 5° to 250° C. for a period of 3 minutes to 80 hours and then treated with at least one of hydrogen, oxygen and steam at a temperature of 350° to 750° C. under a pressure of 1 to 50 atm. (absolute) until poisonous materials deposited on the catalyst are eliminated.
 6. A method for reactivation of a platinum group metal catalyst which comprises contacting a platinum group metal catalyst lowered in the catalytic activity as the result of having been used for partial combustion of hydrocarbons or alkanols with an aqueous solution of a reducing substance in a concentration of 0.01 to 10% by weight at a temperature of 5° to 250° C. until the catalytic activity of the catalyst is substantially recovered.
 7. The method according to claim 6, wherein the reducing substance is a member selected from the group consisting of hydrazine, formaldehyde, sodium borohydride, lithium aluminum hydride, sodium tartrate, potassium tartrate, sodium potassium tartrate, calcium tartrate, sodium hydrogen tartrate, sodium formate, potassium formate, calcium formate and glucose.
 8. The method according to claim 6, followed by treatment with at least one of hydrogen, oxygen and steam at a temperature of 350° to 750° C. under a pressure of 1 to 50 atm. (absolute) until poisonous materials deposited on the catalyst are eliminated.
 9. The method according to claim 6, wherein the catalyst is previously treated with at least one of hydrogen, oxygen and steam at a temperature of 350° to 750° C. under a pressure of 1 to 50 atm. (absolute) until poisonous materials deposited on the catalyst are eliminated.
 10. The method according to claim 6, wherein the catalyst is previously contacted with an aqueous solution of an inorganic alkaline compound of an alkali metal or alkaline earth metal or mixtures thereof in a concentration of 0.001 to 10 N at a temperature of 5° to 250° C. for a period of 3 minutes to 80 hours and then treated with at least one of hydrogen, oxygen and steam at a temperature of 350° to 750° C. under a pressure of 1 to 50 atm. (absolute) until poisonous materials deposited on the catalyst are eliminated.
 11. A method for reactivation of a platinum group metal catalyst which comprises contacting a platinum group metal catalyst lowered in the catalytic activity as the result of having been used for partial combustion of hydrocarbons or alkanols with an aqueous solution or a reducing substance in a concentration of 0.01 to 10% by weight at a temperature of 5° to 250° C. for a period of 3 minutes to 80 hours and then treating the catalyst with an aqueous solution of an inorganic alkaline compound of alkali metal or alkaline earth metal or mixtures thereof in a concentration of 0.001 to 10 N at a temperature of 5° to 240° C. until the catalytic activity of the catalyst is substantially recovered. 